Thanks guys that's a huge help. The bike I'm looking at is online at Performance Bicycle. It's a GTw Avalanche Expert. It is women's specific bike/frame. The tech guy told me definitely a medium. The bike I was looking at in the bike shop was a Specialized Myka HT Elite 29er. It's the only one they had in the store and it was a large. And they suggested without a doubt that she would need a large.