Personally, friends is the one thing that I don't think should be taken into account (and we haven't). How many friends do you still have from primary school? We move on. While it's nice to have a friend to share the new experience with, kids make new friends at secondary as well, and it's far more important to be in the right school for the child in other ways.
But deciding the right school isn't down to ofsted ratings. The things we've looked at is: subject choice (I actually prefer fewer subjects to be available, the traditional basics that will take you anywhere, rather than photography and drama, but your views will vary!), size of class, intake to year, extra-curricular activities (this is where I like drama!, music, sports), trips available, teacher retention (I think it says a lot if teachers hang around), teachers caring enough about the school and kids to do extra stuff with them, access to the Head (often in bigger schools you deal with HofYear only), what kids who are there currently think of the school/teachers, and what recent leavers have to say, etc etc.
My oldest is at Grammar - the very academic one - which we favoured for her because she's quiet and conscientious and we felt she'd be overlooked in local comps, but would have done ok. She loves her small school (90 per year), and they really notice her and encourage her to have confidence in her abilities. She's not competitive, and doesn't feel pressured, but she does work hard, harder than she would at comp because it is expected. She was lucky in that her best friend went too, but she would have gone anyway.
My next has just passed too, and will go to the same school. I think she would do well anywhere as she is much more outgoing, loud, confident, and I wouldn't have minded where she went! Looks like she will have a most of her friends going too, so quite different to your girl. She is quite competitive, and I think she'll find some like-minded kids.
My 3rd will be doing 11+ next year - we'd like her to go to same school too (but you have to get the highest marks when you live out of catchment, no sibling advantage, so it is not easily achievable). She is more like the 1st, but with the added element of being more inclined to be distracted by silly friendship stuff (which has improved through primary!), so I'd like her in a school less chance of falling in with the wrong crowd, and high expectations throughout. She is unlikely to have any of her close friends going, but she is keen and excited to go. We've always emphasised that it can be good to have friends at other schools for when you find it tough at your own! If she doesn't get in there, she'll hopefully go to the only-have-to-pass Grammar, which is also a fab school. Swings and roundabouts on the advantages/disadvantages, bit further away, bigger (150 per year).
That was an essay! In summary - "ultimately we want her to be happy". She will be happy in the right school environment for her, and will make friends there, and happiness comes best from working hard and achieving what we can.... and the label grammar/comp doesn't make a difference in that, it's what each school has to offer your child that matters. I wish you well in coming to a decision you (and she) are happy with. It's not easy!