I dont think it is too late :)
Personally if some kids were bullying my kid..
i wouldnt send her...
i got bullied and i was very unhappy at school..
so i couldnt put my little one through that..
also they may still let her sit her gcse's even if you pull her out..
i got sick my last year of school and didnt attend school much at all
after that... they still allowed me to sit my exams :)
i got into college even tho i never attended my last year.. :)
its surely possible :)
and she will be far happier therefore more likely to get good results..
she is safer at home in my opinion ..
bless her..
i understand what she has gone through...
Good luck :)