I’m getting mixed signals…what do I do?

So I have this friend and in the past 6 months or so, we've gotten pretty close. We're both part of a larger friend group but we often hang out just the two of us and I absolutely adore her. However, the past month or so she's stopped texting first, gotten extremely dry in her responses (and that's if she even responds to whatever I sent), stopped liking my instagram posts and never even views my stories anymore.

Whenever we are together she just kinda acts like- why are you talking to me. For example, we went to prom and I tried to hang out with her but whenever i'd say something to her she'd look at me like 🤨, and she kept walking away from me to talk to other people. She also danced with literally all of our other friends EXCEPT for me, and it was clearly on purpose.

Those are just examples of how she's been treating me overall, and I'm not gonna lie...it hurts!! Is she mad at me? Did I do/say something? Does she hate me? If so, why?!

I have absolutely racked my brain trying to figure out what the heck I even could've done to cause this, but no matter how much I replay in my head, look back at our messages, and just think I really can't come up with anything. I've even asked my mom if she thinks I could've done anything to cause it and not even can think of anything. It's as if she suddenly hates me. We used to go to the same school so could someone have maybe told her something about me that isn't true? (i got heavily bullied by a group of people there and they still don't leave me alone, so it's possible) She's also started hanging out with a different friend group that some of the girls that are in there are so sweet, but some of the others are...a bit strange (they kinda give "mean girl" vibes. They gossip about people 24/7).

Sorry for the long post but how should I move forward with this? I'm not even sure if it's intentional. It's our senior year but we're not going to the same college...so should I just give up? Idk.