It is going to be magical no matter what. If you plan to do a character meal, maybe schedule that on her birthday. Or plan to do the rides she is most excited to try that day. You can't go wrong; there is literally magic around every corner even on the "average" WDW trip. As a first timer, she will be blown away regardless. Or, you might want to consider paying extra for a pirates and pals Wishes cruise, or the new Tiana Riverboat dessert party coming to MK if those are things she'd be interested in. I don't think spending extra money is necessary, however, given that it's her first trip and nothing is going to feel commonplace or "been there, done that" to her.