God No. I wouldn't. Ds1 is currently year 10, 1/2 way through GCSE's.
I would speak to head of year, and also tutor. In fact I would probably email them now, over Easter, now and ask for a meeting ASAP, ie Tuesday.
She Need help and support.
but you know, there are signs, girls can be bitchy and you can be very happy one minute and fall out the next as you've clearly seen - she was happy in year 9, now she's had a falling out.
she's had some problems before, which school probably didn't deal with very well?
but she was happy in year 9, so take comfort from that.
so she needs to learn to ride the storm, the latest issue, and you need to help her, and you yourself need help and support, to allow her to be able to do this.