I'm looking for a book but I can't remember the name.
Could it possibly be Wings, by Aprilynne Pike, or its sequel Spells? The first is where a teenager named Laurel has a "zit" that grows out of her back into a flower, leading her to discover she is a faerie. In the faerie land (called Avalon) she meets and is attracted to Tamini, who acts as her guide. The second book is where she goes to the Academy of Avalon, and sets up a love triangle between Laurel, Tamini, and her human boyfriend, David. Trolls are the bad guys in the series.
If neither one of these are it, we'll keep looking. Thanks for your question!