I had a 599 and it was a great bike if you like an inline 4.
I know there are a lot of girls who ride SV's but they seem really tall to me. I could just flat foot the 599 and I'm 5'9 and all leg so I am not sure if she would be comfortable at 5'4. But like I said, there are a lot of short girls that ride SV's and don't seem to have a problem.

I never rode on the back, so I can't speak for it's comfort.
Cheap