It sounds like she likes sweet fruity florals? Maybe something by Lolita Lempicka (easy to find at Sephora) -- those are supposed to pack a wallop.
Nina Ricci Nina is another sweet apple scent with several flankers -- I don't much like sweet and fruity, but I kind of enjoy this one (which might mean it won't be sweet and candied-fruit enough to please your girlfriend), and it seems to me to last pretty well. It also comes in the loveliest bottle ever!