Mainly, a very upright shoulder, she's a tad light on bone, and her hindquarter is a bit on the small side (but with good angles, so it might muscle up nicely and look balanced). Plus the narrow chest. These are all fairly minor flaws, the only thing that might affect her way of going is the upright shoulder and even that shouldn't be much of an issue with those lovely pasterns. She's also a wee bit weak through the loin but that's a "nothing" issue unless you want her to be a weight carrier in which case then the light bone would be a problem too.
The narrow chest may make her a little more likely to knock herself as she moves, but contrary to popular belief, has little to do with heart and lung room.