Okay, this sounds good. I know she's going to call me out on it within a week though, she calls me out when I'm quiet in class for just one day. And if I say I've been busy, she won't believe me and she'll keep pushing, so I don't know how to handle that. I'll probably just keep insisting I've been busy, because I don't know if telling her what the problem is will be good or bad. I guess I'll cross that bridge when I come to it.You don't have to burn the bridge, but you shouldn't invest anything more into what doesn't seem like a genuine friendship. Dropping this friendship might hurt her feelings? She didn't seem to care what stringing you along for months might make you feel.
Just don't actively engage her. You can downgrade her to acquaintance without being hostile. Greet her when you see her and nothing more. Just give her short succinct but courteous answers if you want. If she txts you and you choose to respond, you take as long as you want to do so. If she calls you out on why you're taking too long to answer, you tell her you've been busy. You can maintain your illusion of friendship if you really want.
This isn't about being spiteful or resentful. She is the source of your pain right now and you need to distance yourself as much as you can. For your own sake.