Don't discount the Prestwick flying club.
There instructor base is quite unique in the UK.
You have university boffins through to very senior airline examinors. You might have issues with fitting in lessons etc but for building the foundations of a life time of flying your really going to struggle to beat it. The PPL's I have flown with from there have not been to far off Commercial standard and have a very solid grasp of the basics.
I wouldn't worry about being the only young girl about either, I wouldn't have thought being a dippy chick will do her any favours. But if she is keen, polite and not discounting fun I wouldn't have thought she would have problems.