My (18F) best friend (18F) of 6 years hasn’t communicated with me for 8 months since she said she needs some time for herself

My best friend and I have been super close for the past 6 years. Maybe not always best friends, but best friends for the majority of it. She’s a very anxious person who often takes breaks from social life when things get overwhelming. The longest we haven’t talked before this though was about a month after a very big fight, but often she still talks to me here and there even during these breaks.

About a month before she left this time around, she expressed we haven’t been talking as much and we quickly fixed that as we started talking every night, and having lots of fun together per usual.

Some stuff went down this summer and her boyfriend did some unacceptable things to both of us, which hurt both our trust toward him as he was a dear friend even prior to their relationship to both of us. I soon made up with him since she never expressed she needed me to break things off with him and only seemed sceptical for my own well being. Though, we had fun per usual and were super close for a month after these incidents, so I do not think this was the tipping point.

As the school year started, she decided to take a social break from everyone other than me, and I kept her company. Soon she said she wants to be fully alone for a while including me so I left her be.

However, it has been since September that this had happened. She first said it was school stress briefly, then that it was about her and her personal issues. These revelations happened during one text conversation where I called her and asked if we could talk briefly. It is important to note that she still answers to calls but each time ends calls short by saying she’s not ready yet (she knows it’s me calling, has my number saved).

Another two important things to note – everybody else close to her as far as I’ve heard hasn’t interacted with her much in a while either, and most of them still think it is school stress. I did on one instance run into her at the bar for an awkward encounter, but she was with her friends who came to visit from another country so it is still possible she just went out because it is a once/twice a year opportunity. I also heard she goes to the local tea shop still, but that could very well be her waiting for her dad to pick her up after school, not her going out socialising per usual. All her classmates say she looks very off and is antisocial at school as well.

I don’t quite know what to do or where to go. She is still one of the people I cherish the most and I would do anything to get her back or at least get closure. And yet I can’t bring myself to call her or ambush her in front of her school and ask for closure since
a) it would make her anxiety act up I don’t wanna make her feel that bad because I love her
b) I fear it would close every chance I have of her coming back if this indeed is just a phase

I really wish I could help her, but also selfishly wish I had her back…

TL;DR
My 18F anxious 18F best friend of 6 years hasn’t talked to me outside of brief calls she ends quick when I call her in about 9 months. I’m not sure if our friendship is over and don’t know what to do.