I suggest picking the best related episodes from the new seasons, so that she can get a feel of the different doctors early on. This is basically what I did, I started with Blink. Time of Angels, Flesh and Stone, Silence in the Library, Forest of The Dead - So that I got to compare Tennant and Smith, as well as the reactions of other characters to the doctor, being River Song and the Angels.

The two-parters also have the kickass parts when it shows that the doctor, goofy looking thing that he is, is one of the most feared beings in the cosmos. 11th hour is also a good starting point. The "Basically, Run" scene was awesome. And little Amelia is loveable. I think I like her more than adult Amy.