Context: LTR for about 5 months now. She was a plate/ FWB for over a year until she asked for commitment and I said yes.

Now: I'm thinking of ending things with her because I smell something fishy about one particular guy, but I don't have any evidence.

I set my boundary pretty early on that I would NOT be in a serious relationship if she hangs out with male friends alone and she agreed. I still see text messages from ONE GUY pop up from time to time and asked her about it - she said he had been friends with her for a long time and when she was very depressed, he listened to her (sounds like an orbiter). Now that she's in a LTR, she only replied out of courtesy and never agreed to meet him one on one. She showed me the messages so I stopped it there.

Still, I suspect they are still meeting - because today she suddenly changed her routine schedule (she would meet me at my workplace around 2 in the afternoon and give me my house keys - she likes sleeping in when she stays over. Today, she suddenly drops by at 10am and I only saw her missed calls at noon). I thought she went back to her place but she didn't. She was at a cafe somewhere near my place and met me for lunch.

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. She's telling me that it's enough for her and thanked me for everything (sounds like she's breaking up). I was like What the fuck? A very big overreaction over something so trivial. She could have just answered, but it became me not caring about her and making her cry.

It got me suspecting, because I can tell she was out somewhere and possibly seeing somebody. Before we met for lunch, I asked her where she was and she didn't answer, instead asked me why I was acting strange. I suspect she's blowing things up over her work schedule to distract me from this.

I don't want to be too controlling, I just set my boundary and told her it's over if she crossed it. Now she's gaslighting me over this shit and I'm quite fed up to be honest. I told her to just go home and rest and we'll talk later.

Am I handling this right? Am I overreacting? (actually I didn't react much to her being upset, but I thought this is ridiculous). Should I plan some gotcha questions to see her inconsistencies?

If I'm not overreacting, how should I break things up nicely with her when we next meet?