Purchase yourself the three volume series: Principles of Conformation Analysis by Dr. Deb Bennett
Those will explain conformation in detail and biomechanics, and how it all works together to create movement and such in great depth.
Overall she's a well-structured individual, but still racy in her conformation, which goes against you as a riding mount. In particular she is downhill built and has a high hock and stifle set. The only other thing is that her neck is set low and roughly connected. You can see by her neck musculature (the bulge at the lower cervical curve), and how she carries it in the trot videos that she doesn't lift her base of neck, but instead drops it and roots it. As long as she does that, she'll never come through from behind.