What Causes Short Torso With Little Space Between Bottom Rib And Top Of Hip?

I am a 22-year old female, and I've always accepted my figure as "boyish" because I have a very short torso with about an inch of space between my bottom rib and the top of my hip (I'm 5'7"). When I attended a fitness class the other day, I was unable to execute a certain exercise due to the fact that these bottom ribs were "blocked" by my hips if I moved that certain way. No one else in the class seemed to have an issue. I was wondering if I might potentially have an extra set of floating ribs, or anything about my anatomy might be "off" because of the very little space I have between my hips and ribs. I never really cared or noticed until I realized there was a certain movement that I couldn't perform in comparison to other people.