I would also pass. Her hind right hoof looks suspicious to me. I really think that it's clubbed, though I'd need more angles to know for sure. There's definitely something wrong with the angle though. Whether that's genetic or bad shodding, I don't know.
Her LS joint placement are far from ideal and I don't like the angle of her hips or her shoulder. And I think that both of those are combining to give her a very choppy, fast gait rather than a smooth, rolling one. She looks as off balance as my OTTB did fresh off of the track at the canter. The trot was marginally better, but that canter still bothered me.I know that you said you liked her gaits, and maybe they're better in person or in the saddle, but I can't imagine her being a smooth ride. She was very fidgety and really just didn't seem to want to use her body. I'm not sure she even can, with the lack of muscle that she's displaying.
Add that to the fact that she's probably 30 pounds underweight and needs months and months of flatwork before she should be jumped, and I really don't think she's going to suit your needs. She doesn't look like she's feeling very good and that's probably part of the reason for the lack of 'umph' in her gait, but that may or may not be fixable. Once she's conditioned and on a good diet (and she sounds like a hard keeper which spells m-o-n-e-y) she MAY be capable of lower level 4H or something, but I can't even guarentee that.
IMHO, I'd pass her up. She isn't spectacular and seems to be lacking some basics somewhere, and then there is her health. If you did buy her though, immediately put her on some better food and condition condition condition. I can't tell you much about her jump except for that it lacks scope that I would generally expect to see in a hunter jumper.
That aside, did anyone else get the dramatic feeling of expecting something bad to happen with that crazy symphony music on the jumping video? XD