She is very cute! You could be close to correct on your guess of breed mix. Her body structure is light. Right now she is rump high but that could change as she develops. It looks like maybe she needs a little more heel (in the snow photo she looks a little low). Truthfully it is hard to see faults from your photos as she is not standing square. Personally I don't see anything I'd be concerned about. She sure has a lovely face.
She looks like a nice pleasure mare to me. What is your main interest as far as activity?
Welcome to the forum!!!!!
If you ever find yourself in a fair fight, it's because your tactics suck. ~ Marine 1SGT J. Reifinger