She is MILDLY calf kneed, if you ask me. If she has been trotting along all this time without lameness, then you should trust that she can continue. She has heart! Think of Seabiscuit; too small, not well put together at all. Didn't stop him.
Gidget is very tidily built, all in all. I would perhaps not use her as a jumper, but the more you work on building her hind end and getting her to USE her abdominals to raise her back and step under, the more weight she will carry on the rear.
Stick with the hill work, transitioning up and down, halting and backing up the hills and stuff like that. Have faith, someone exagereated.