I don't censor the stuff my kids read. I generally like to read what they read and then discuss the books with them, especially if I have any concerns about something in the book (such as the way Edward treats Bella.) If you didn't have a problem with the sexual undertones or violence in Twilight, then I doubt you'd have a problem with anything at all from the "YA" section of the library or bookstore.
I wouldn't allow my children to read anything pornographic; if it can't be legally sold to minors, I won't let them read it. Other than that, I don't have a problem with any books they select.
As for suggesting good series, it depends on what kinds of books your 7th grader likes. DD2 likes fantasy books while DD1 prefers realistic books- and sometimes we'll find something they both enjoy (particularly if it's a fantasy series set in modern times- although the Eragon series is a huge hit with all 3 of us and it's set in another world equivilent to Earth during the Middle Ages.)
DD1 enjoys anything by Caroline B. Cooney, along with random other books selected as she wanders through the library. DD2, my fantasy lover, enjoys Eragon, Harry Potter, Leven Thumps and the "Foo" series, "So you want to be a Wizard" series, Pendragon, anything by Cornelia Funke or Tamora Pierce- and probably others that I can't think of right now.
OK, I just re-read the OP and realized that this is for a gift, and you want to purchase something rather than take the child to the library. In that case, I'd suggest a gift certificate to a book store, and let her select her own book(s). You might accidentally select something she already owns, or that isn't quite her taste. It's hard to guess her "style" of books from Twilight alone- she might like the fantasy/supernatural books, or she might like romances. She might enjoy any kind of vampire book, or she might be such a Twilight fan that she couldn't enjoy any books that portray vampires differently.
