How many times has she been before? If not many, she probably won't be bored. My DD is 15 (we have gone at least yearly since she was 3) She loves the rides at Hollywood Studios like Rock and Rollercoaster and TofT. Space Mountain at Magic, Everest of AK and Soarin, Test Track, Mission at Epcot. She also likes to spend a lot of time at Epcot in the different countries. It will be more fun if she has someone to go on the rides with. Depends on how long you are planning to stay. 2-3 days and she won't have time to get bored. There is always DisneyQuest and Waterparks but if it's budget, that's an added expense.
My niece goes a lot (season pass and they live an 1 1/2 away) she doesn't seem to get bored either. She's gone there on field trips too.