Yes. Sticking it out until GCSEs is good advice.
Start researching post-GCSE options together - it makes it more positive; it gives her some control; it gives her buy-in; and if she needs good grades for a school she likes, it will be an incentive.
Never underestimate humour - celebrate completed weeks at school with things like a cake and candles - or whatever floats your boat. Congratulate her for her resilience and common-sense in sticking it out. Find positives to celebrate.
I hated my school. I coped by focusing hard on what happened next - and what I needed to do to get to next.
And even though I hated the school, there were positives, and I focused relentlessly on those.
And next does arrive. And it is often even better than you thought it was going to be - especially if you've put some work into making sure it is.
She can do this. She's resilient, strong, bright - and that kindness implies a fundamental openness towards other people and experience. She has many, many resources to draw on - both from within herself and from her family.
This is a blip - she'll get through it. And she'll make sure what comes next brings her joy.