Cocktail Queen:
I think the issue is what are her next options. Here in Birmingham there definitely is a sharp divide in the quality of senior school education between grammar schools (which are state funded, so free to pupils, but places are based on your scores - highest 600+ scores get into the 5 grammars).
My DD1 wanted to sit the 11+ (which ultimatley was not a success - she's missed a place by about 10 pts) but mainly because her great friends were and she wanted to carry on going to school with them. We couldn't afford tutors, they could. They got in - we didn't. May or may not be related - DD1 is bright but rushes and refused to write down her sums so frequently makes simple mental arithmetic mistakes that had she written down all steps for her problem she would easily have caught. The tight timings of the 11+ probably made her feel even more pressured (most children didn't finish maths sections) - so I suspect it all went awry there.
My advice is this:
research & discuss the benefits of grammar school education vs. comprehensive in your area. (Here 90%+ pupils in a grammar go on to Russell Group universities / ~15% from a comprehensive). I have no idea what my child will want to do at 18, but I was concerned that not going the grammar school route would narrow her options (hello hair dressing/ catering school). It's clear that Cambridge/ Oxford options happen for Grammar students but are way out of the norm for ordinary comprehensive kids in Birmingham.
Visit the school(s) - DD1 could see clear differences between the comprehensive she's now going to go to and the grammar schools. Clean & pleasant environment vs. run down and a bit down at heal being the obvious one. She could see for herself the advantages of going the grammar school route.
Sometimes going the grammar route is about moving away from bad influences. (and that can be desirable - certainly many parents of quiet, studious boys are desperate to get them into the grammar system and away from bullying/ peer pressure)
Comprehensives have their good points - a full spectrum of abilities, interests and normal slice of the community - and that can be beneficial. In our case, we're fairly confident (and the school has also indicated) that DD1 will be placed in upper ability groups (possibly top set for maths) - so the benefit of being the big fish in the small pond, which can give a child a lot of confidence. And that could be the most beneficial thing ultimately.
Finally - oddly enough - in terms of sport opportunities the comprehensive is better than one of the grammar schools we saw (recently co-ed but nearly all teams (rugby, tennis, cricket, soccer, etc...) were only for boys - girls teams just weren't available). And I suspect this is what will please DD1 about going to her new senior school (the comprehensive near us) as she lives for her sports.
Much like chosing which primary school to go to - chosing senior school is a big decision made more complicated by the fact that you want so much to be right now - education, developing concepts of independence, self-worth, identity, etc... and ideally a positive experience which helps the child reach their potential. For us educational attainment is part of the equation - but every child/ parent will have their own priorities.
My advice is visit schools, talk to your DC and keep your options open right until you absolutely have to make a decision (especially as 6 months from now her friendship groups/ priorities/ and opinions may be slightly different).
HTH