She sounds very similar to DD when she started secondary, like many autistic girls she fell apart gradually.
She went from a fairly happy smiley girl to withdrawn, stopped speaking, not smiling ever, loads of OCD around clothes and her bedroom (god forbid the duvet wasn't straight).
We tried to get help but she's non disruptive and flies under the radar, eventually we moved her to private school and she's honestly a different child in the first term she was photographed smiling at an event and my heart broke.
She now has a lovely group of friends, talks too much in class, sings and dances in all the performances and is a well liked member of school.
That's not to say she still doesn't show signs of being autistic just that she's in a good place so the outward behaviours are greatly reduced, always remember behaviour is communication.
She was diagnosed at 8 but I would have missed it if it wasn't for the fact that our nephew is autistic and I had one light bulb moment when she couldn't understand why someone would be upset.
She's shown sensory issues all her life (some are only noticeable with hindsight) and has always been stubborn.
Don't be fooled into thinking autistic girls can't be social or won't have many friends, they can and do equally some are very happy without many friends every child is different.
It's so hard when they are clearly in distress and I hope your daughter finds her peace.