i think she'd love an email or a letter like this. especially since she's still a student and still starting out. at my uni, we go into psych because we want to help people out, but we spend the whole training program worrying that we haven't helped, or helped enough, or even done harm. a simple thank you can mean so much.

like the others have said though, do send it so long as you're comfortable that she may not be able to reply.