Buy her something just as expensive that she'll like...
?
Best advice I can give is buy something that you can easily get parts for. Yes, Traxxas is HUGE, they're sold in nearly every hobby store in the U.S. and then some. They make excellent bashers. Not so great on the racing circuit, although the Slash took the RC world by storm when it came out. A lot of racing clubs made up a Slash specific class because so many people wanted to race them. Not sure how well those are holding up against the competition from Associated, Losi and the like.