J.S.
I had a late walker-he didn't walk independently until 18 months. Although, by 15 months he was moving forward on his belly (army crawling). We did physical therapy, and some questions the physical therapist asked were: can she support her weight while you help her stand (if she can't, it could be a problem), can she get from sitting to her tummy or vice versa, how much tummy time has she had, what does she do when she's on her tummy?
I would definately follow through with the physical therapy evaluation-we did physical therapy for about 4 months, then he started walking and slowly caught up. He's 6 now, and you'd never know there was ever a problem. He plays soccer and baseball as well as all his friends.
Some of the things we did with him were: kneeling and playing at a low table, practicing lots of pulling up-he started by sitting on a low bench and pulling up on our train table, rolling on his tummy on a big yoga ball, and forcing him to spend time on his tummy (he hated it!).
It sounds like, other than gross motor, all her development is on target. I wouldn't worry too much, especially if the pediatrician isn't very concerned. Work with the physical therapist and I bet she'll be up and running within a few months.