Autistic shutdown or depression?

Hello, I'm new here and would really appreciate some help or advice.  My daughter is 15 and we've just started the process of diagnosis for ASD.  Over the years when she has struggled to cope with life she has had chronic tummy problems, pulled her hair and cut herself. She is currently controlling those urges but has recently displayed new behaviour which I have not seen before.  As she finds it hard to be around many people, lockdown suited her fine and the return to school has been overwhelming.  In the last few days, once home she has become very upset (sobbing, hitting herself, saying she can't go on) and then going into a trance-like state where she is unable to speak and barely move, after which she is exhausted, even the next day. Up until today she has made it into school, but this morning she managed to get up and dressed then stood at the top of the stairs, weeping and looking almost asleep, so I told her to go back to bed and she has been sleeping ever since.  Obviously as a parent it is very distressing to see your child so unhappy, but also this new "shutting down" behaviour is quite frightening.  Afterwards she said she could hear me but it was kind of muffled and far away.  I am at a loss to know what to do and how to help her. I am waiting for a call from the SENCO at her school to see what they can suggest to help her, but in the meantime I am concerned she is retreating inside herself more and more. I would be grateful for any thoughts or suggestions.