Get the truck that suits her experience level and you can afford. Don't buy her some 70 mph truck for a first. Not unless you secretly expect to inherit it. One of the HPI's or Traxxas RTR's would be fine. Plenty of replacement parts and knowledge out there. I would mention, I have two Traxxas's, but HPI is coming out with some nice stuff now.
OH, and to make things easier on you, get her an electric.