She is very pretty and she has really filled out since even your first pictures last August. I noticed "Three Bars", and my QH "Ro Go Bar" (1982-2009, RIP) had a similar build. He was a grandson of "Go Man Go."
If she is like my QH she should have a very pleasant sitting trot. But he was built downhill and couldn't really jump--more of a fast pleasure horse. He was also very lazy, but, after some reassuring by fawning teenage riding students he became a wonderful and quiet babysitter horse, at 15'3hh. I agree with waiting to back until next year and take it slow. Ro Go Bar had those TB legs and big feet. You wouldn't want to work her hard until the bones are set. =D