Awesome!
I like GT's mountain bikes, given the prices, even if they do seem to run big. Do you happen to know the model year? GT's catalog archive only goes back to 2009. The current Aggressor's an entry-level mountain bike.
Also, your mom might consider getting a new helmet. I'm not a huge fan of the idea of second-hand helmets. The styrene degrades over time, and you don't know if they've ever been crashed or dropped.