My wife has been riding on a small cruiser (Savage 650) for a year, and recently was trying to get accustomed to my Bandit 600. She found the Bandit very tall and heavy compared to Savage. She felt more confident on the lower sitting cruiser, and therefore she lacked enthusiasm to make the switch to a sportbike. Then I picked up a 2001 SV650S. She liked the low seat on it, and after riding it a couple of times, she fell in love! That bike handles so nicely!
That said, I think SV650 is a very powerful motorcycle. More powerful than the Bandit, and I had felt a few times that Bandit had more power than I could handle in the beginning. SV650 makes my butt slide backwards on the seat when I accelerate. Then again, I probably would not whack it like that if I were just starting out. Your sister, lacking the testasterone that kills so many young men on fast bikes, may just be fine on SV650.
Man, that bike is so frisky! I still can't get over it... Which reminds me, we are going to be putting up that Savage for sale pretty soon. Makes a great starter bike!