Just two days later she calls crying and saying im horrible for stringing her along for a year and making me feel guilty and shit.

urgh..... don't like that emotional blackmail shit

Than soon later she switched it again and said she doesnt want anything serious, but now that ive said it (that i dont want anything serious), it made her feel used and she needs to hear it from me that im serious with her. I honestly dont even know what she wants right now

She wants commitment, but when she gets it she will get bored and fuck you over.

my answer / it feels like its time to call it. I want a casual relationship right now but she needs reassurance about the future, so it looks like theres no way to continue

Yup.

It does look like an impasse. A small hope to keep the plate spinning could be to just be very kind, honest but firm and see what she chooses. Still probably just leads to a mess though. Its so hard to be kind and firm when they start bitching at you over something emotionally. Even if you manage it, she will always be wanting more.

Yeah I've been with a girl like that.

They're #1 torn between finding you attractive, fun, exciting and ability to get them off when horny on one hand vs. #2 you're making them insecure, feel anxious and desire love/stability/affection on the other hand.

When they're leaning more towards #1 at any given moment, and give in to those feelings, they will call you and be fun/lighthearted. When they're leaning more towards #2 at any given moment, and give in to those feelings, you get a serious conversation with a lot of crying, they threaten to (or do) break up with you. Only to call you again when they lean more towards #1 and say they over-reacted and apologize.

Basically what I'm saying is, that once this cycle has begun, it's a trade-off between pussy vs headache.

This is also the reason almost all plates sooner or later break. The only way to somehow escape this is to be 1) So attractive in an unique way that girls won't believe they can replace you and 2) having the skill to make them feel satisfied in terms of affection/love even though you still see other girls.

Most men can't even spin plates, and it's a very rare man who can spin a plate indefinitely. It probably also depends on the girl a great bit.

Just two days later she calls crying and saying im horrible for stringing her along for a year and making me feel guilty and shit

Classic manipulation tactics. She's an adult, and you didn't decide for her to spend a year in something casual. Any time someone's trying to appeal to guilt or shame to get you to do something you don't want to, they're trying to manipulate your innate, nature given male soft spots. As a woman, she's evolved to do just that. Don't think too much of it, and definitely don't let it be the judge of you.