Depends on the secondary school. Our Year 7s have read things in class but there has been no reading list or real requirement to ready anything else, although teachers do try to encourage independent reading and they have regular reading lessons as part of English.
How about trying your daughter on some more old-fashioned stuff if you haven't already. Things like the Anne of Green Gables series, Little House on the Prairie, Pollyanna etc.
Or Susan Cooper's Dark is Rising series or Ursula Le Guin's books if she likes fantasy. Not more grown-up as such, but just a different approach if she mainly reads modern stuff. Still on the fantasy type, there is Eoin Colfer - the Artemis Fowl books are good, while The Supernaturalists is probably an 'older' read. Or how about Philip Pullman's Dark Materials trilogy, excellent stuff that an 11-year-old who reads well and enjoys reading should be able to tackle.
How about something by Lynne Reid Banks - some are definitely for older teenagers, but some would suit an 11 year old. Or Judith Kerr's 'When Hitler Stole Pink Rabbit' and the other 2 in the series - really great stories (based on real life) about a Jewish girl escaping Nazi Germany and eventually coming to the UK.
There are Caroline Lawrence's Roman Mysteries books - they are now being televised, so she might have seen them. Or Jostein Gaarder's books, some are a bit older, but she could probably cope with the Solitaire Mystery and some of the others. Some are fantasy or mysterious, some are philosophical.
Most girls of that age would also like anything by Ruth Thomas or Eva Ibbotson. Or how about Sylvia Waugh's Mennyms series - a great set of books about a family of life-size dolls who are 'alive'. Or just about anything by Leon Garfield or Joan Aiken Hodge.
How about Anthony Horowitz - the Alex Rider books are quite a decent read, but a bit gadget-full and high-speed-chase for my liking sometimes. Even better are his 'Power of Five' books, starting with 'Ravensgate'. Really cracking stories, well told and good characterisation. A bit 'dark' but if she's reading and liking the later Harry Potter books she should be fine.
Or there's the Flambards books by K.M Peyton - even got some horses in there!
Or if you want real teenage lightweight trash, try the Princess Diaries series. Real rubbish but girls of that age and above like them!
I'll have a think of some more, but why not have a look in your library? Ours has a big folder with lots of different suggestions for the various age-groups.