Sounds like she is concealing something from you, which means she does not respect you.

You blue pilled.

The fact that she blew up over her work schedule like that, is exactly what you thought. It's misdirection, to take focus away from the topic. That's all you need to know. She may have spent a platonic afternoon with this guy as an emotional tampon or got railed all afternoon by a different guy.

It doesn't really matter, if this is how she treats you. She broke your set boundary. Done.

Vetting takes , years. 5 months in a LTR, is not really an LTR, especially since you don't even live together.

Im no expert but what i see is 1.) You have oneitis because you wont stop talking about her and what she's doing where she's going. So that could be part of the problem 2.) Your gut is telling you she's on some fuck shit. 3.) Her emotional outburst (in my experience) is a way to divert attention when they are wrong. She cant tell the truth or argue so she has an emotional outburst and makes it your fault. If im in your shoes I would probably lower my attention and interest in her and do anything you can to verify. Her breaking up with the "thanking you for everything" means you cant really have ltr with her anymore too or she'll see you as a bitch. Its a tough situation and its why i hate LTRs as i get older lol. Interested to see what other guys think is best course of action.

In my personal experience, when they blow up for no reason when only very lightly questioned it is a major warning sign. Check its not PMT time. If it is, then try again later with similar questioning and see what happens. If there is no hormonal reason for anger then be alarmed.

Most likely you frightened her by getting too close to something uncomfortable and her reaction was to blow up. This often happens with women who are experienced with manipulating men. Usually sexually experienced women but it can just be a daddy's girl who learned it was a way to shut daddy up. They know that men back off angry women because men know they can never get anywhere constructive with angry women, so she acts up and it shuts your questioning down. She then relies on your thirst to drive you back to her and patch it all up again.

If this is what is happening, remember; THIS IS NOT A SHIT TEST. THIS IS BEING SHAT ON.

Did you do anything unreasonable? If you didn't DO NOT APOLOGISE for upsetting her. This plays right into it and shuts you down for looking into it again. This is a common mistake. They guy wonders how did his nice girl suddenly get so upset and thinks "well it must be something I did wrong. I want pussy tonight, so I will soothe her". Once you apologise for rational behaviour, you are doomed to manipulation.

The irrationality of it all draws you in, you just know something is wrong but you try to get to it rationally with her. Cut right through that to the core issue -she is lying and that is very bad for you. Stay calm, don't argue will bullshit just call it as bullshit, say you need to hear sense, she can postpone the conversation but not avoid it, it must be next on the agenda before any other couple like activity.

If she pulls the "its too much, we need to break up one" -don't get pulled in. You will lose if you try to make sense of it all with her. She will try to lead you a merry dance till you try to soothe her or are too tired to fight about it. This is bullshit. She has you on the back foot with the getting upset trick and you need to get back in control of your life and your boundaries. If she says "I think we should break up" then you need to agree with her calmly. Explain that someone who behaves so irrationally and wants to break up on a whim like that is certainly not what you are looking for, so you back her decision. Make no attempt to reverse your backing of her decision unless she comes and explains the whole thing rationally another time. Coming back, having sex and sweeping it under the carpet will not be acceptable, she must explain why she was so touchy and then you revisit the conversation fully only then will you be her boyfriend again, including having sex with her.

So as to how to break up nicely, its not too hard as its just backing her decision of last time. Just thank her for everything and say you are sorry it didn't work out. If she reopens the argument say It makes no sense to you the way she overreacted but you see the overreaction as proof something was off with the relationship. A sane person would need a very good reason to be that upset over something that you see as normal. So; either you are not compatible and your normal and her normal are too different or she had a very good reason that she is not sharing. Either way you second her decision.

If you go looking for trouble you're going to eventually find it. That's confirmation bias. People with abandonment issues tend to act in a way that ensures that other people leave them. Have you been acting in a way that makes you look low value?

You don't mateguard. It's extremely unattractive and will guarantee a branch swing. Here's the thing: if she wants to cheat, you can't control her. You can forbid her from having guy friends, but she will resent you for that and it won't stifle what she wants.

It sounds like you haven't reached a level of success to have abundance yet. I'm an older guy that's seen this before.

My girl right now is very wantable and social. Guys hit on her all the time. She has guy friends. That's all perfectly ok.

Have you ever been in the orbiter/friend zone before? I have. It got me laid 0% of the time. I got to be some girls emotional tampon while some other guy railed her. If a dude wants to simp, let him simp. You don't have to hear her bullshit. He takes that burden.

My girls father came to visit last year. He asked me "Goon, what would you do if you went to a bar or restaurant with daughter and you got up to get you two drinks and you came to see a guy hitting on her"?

I laughed a bit and of course gave my sly grin. "I would honestly sit back and watch. Let's see what this guy can do. He might get her smiling, or he might crash and burn gloriously. Either way it's amusing to me. At the end of that encounter she's still coming home with me". This surprised my girl's father.

You can make yourself a girls hypergamous best option. You are the best she can find and she knows it without you saying. My girl knows that if she leaves, there's a line of countless women that will happily jump on this dick at a moments notice.

Your other option is to tighten the reins and control her so strictly that she fears you. If she's really submissive she will put up with this toxic bullshit for a few years until her resentment turns in to hatred then she will either try to destroy you and leave or just leave damaged and make the next guy's life hell. Also your connection will never be genuine.

Now, let's talk about your problem. Is it a problem? Are you still getting laid consistently or has the frequency and intensity gone down? Does she still follow your lead. Does she still spend a lot of time with you or has she gone missing several times with no accountability? It sounds like this was a single instance. It's a problem if you see a pattern. And if you see a pattern, address it in a non butthurt way.

Right now you're working yourself up into a frenzy without anymore info. You can dump her, but you're going to have the same issue with the next woman until you learn IDGAF and address whatever insecurities you have.

LTR for about 5 months now.

LTRs are measured in years, not months. If you're measuring in months, just say "relationship" or "exclusive relationship".

As for the actual meat of your post:

Sudden changes to routines are reason for suspicion, and her manipulative overreaction to your question is even more suspicious. A trustworthy person with nothing to hide would have answered your question matter-of-factly. If she starts crying and saying shit like "you don't trust me!", she's manipulating you in an attempt to change the subject and hide something.

There is a very slight chance that there's nothing bad happening, and that her outburst is due to her hormones.

The question you must ponder for yourself: has she added enough value to your life for you to consider that remote possibility, and wait and see? Or would your life be better with an immediate "next!" which is easy enough when you aren't married or cohabitating?

First glance: the schedule change isn’t that sus… seems like she slept over and left a little earlier. Chicks dont get fucked at 10am coffee dates; they get fucked at night before bed.

Cheating likelihood imo pretty minimal.

The outburst is however pretty fucking sus. Could be that time of the month, maybe she went for coffee w Mr beta orbiter and remembered she’s not allowed to meet other men, maybe she’s contemplating monkey branching and went for coffee w another dude.

Time will tell; watch what she does not what she says. Pull back a little and see how she responds (does she chase or does she act unphased).

When I asked her why she changed her schedule today, instead of answering, she got VERY UPSET, crying and explained that today is her day off, that I don't care about her and cannot even remember her schedule

This is a pressure flip. You confronted her with question and she flips the pressure on you to prevent answering the question. If you agree to this, she will use this against you "b/c you agreed to be more thoughtful about her" (or whatever).

She's cheating or is planing to. Demote to plate at best. Your LTR is hiding something from you, this is completely separate from the issue whether you're controlling or not.