Why is my friend suddenly avoiding me? I didn’t hurt her feelings or anything and everything was fine just a few days before it started?

Anonymous
We’ve been classmates for around 4 years, we didn’t really start being good friends until our third year when we began to get closer. We could talk about everything and anything and she has helped me get over my impossible crushes and i’ve helped her mend strained friendships, so i THINK our friendship’s kinda
strong? She’s very comfortable talking and joking about anything EXCEPT one thing; whenever someone even remotely hints at the idea of us being tgt, she becomes unhappy and her vibe just straight up changes in an instant. And this literally only applies to me, like if it was about another guy she would laugh about it, so i’m 100% sure i’m a good friend of hersand she doesn’t want people to make the friendship awkward? I’m fine with that cuz i really just see her as a good friend. However, on Monday, i noticed she was sort of ignoring me, usually she would greet me and stuff but she saw me and just walked past as if she didn’t. Then over the week she was just being distant and avoiding me. I suspected i was overthinking so i didn’t really dare ask her, i thought maybe she was just having a bad week but i noticed she was her normal self around her other friends. So on Friday, i asked her if she was actually avoiding me and if she was ok. She said she was fine and she was indeed avoiding me but it wasn’t my fault, it was just her. So i asked her why she was avoiding me and she said she didn’t know ( I don't know if it’s possible for someone not to know why they’re avoiding another person). But i guess
i needed closure so i pushed too hard? In the end we kind of raised our voices at each other until her friend came by and just told me that i won’t get my answer. I looked at her thinking she would say sth but she just looked away, so i just apologised and left. Just the week before, we were fine and i didn’t do anything to strain our friendship ( at least i didn’t think i did), so i guess i’m just really bothered and confused as to why she would suddenly do this.
Why is my friend suddenly avoiding me? I didn’t hurt her feelings or anything and everything was fine just a few days before it started?
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