I'm a QH person, I don't think her shoulder is too steep at all... the more steep the shoulder, the choppier (is that a word?) the stride, I always heard it, the less slope the better lope...
What you look for in conformation is for the horse to be equally proportioned. Say you take a picture of your horse, chop it off at the neck. Preferably, you should be able to draw 3 O's on your horse's body. One O at the shoulder, one O at the barrel, and one O on the rump. The more equal the O's in shape (more or less oval) supposedly the better the conformation, with a few exceptions in there, smaller front end makes for speed horses, roping, barrels, etc. Short backs, tiny heineys... you get it.
As far as I can tell she looks pretty sound to me. She may be slightly post-legged, but a lot of horses are, and it never really harms their abilities. I think her headset is ok for how she's built, it's a little high, but overall, she's not conformed to doing events where holding the head down low is necessary. If her neck were any lower, it would throw off that beautiful wither she has going on and make her look like she's got a shark fin, which would inevitably destroy her whole conformation.
She's a paint horse. She looks like a paint should. There's a little color thrown in with the QH and TB lines. And she's built like a QH should be.