I've got a ttr230, and I like it a lot, but in retrospect, I wish I had started on smaller bike, may be a 150..
The 230's got great even power distribution, and motos through anything kinda like a tank. Which was (sometimes still is
) sometimes cool in panic-accelerate situations. But sometimes it falls on you, and that can be scary, and can be hard to maneuver on turns, because it's so heavy.
A 230 would probably last her a lot longer before she needed to graduate, but would it scare her away?
I think it depends on her personality a lot, if she's stubborn and aggressive, go with bigger bike. If she's more timid and cautious, go smaller.