She's pretty. Her legs are pretty light on bone and her feet seem really small but that's pretty common with TBs these days. Her pasterns are on the longer side but they have decent angle. I would be a bit leary of doing much jumping at bigger heights but other than that, I don't see a problem.
Her shoulder has good angle. Her head and neck are very refined and attractive. Her back may be just a touch long, but again, not too uncommon and not to the extent that it would be a problem. Her croup has good angle though it is lacking in muscle. It's hard to tell much for certain about her hind legs due to the angles they are at, but I don't see any signs of any glaring faults there.
I agree with SMRobs.. but I see a bit more. I expect her back is a good bit longer than this photo shows. The camera is opposite her hip which shortens her back. BTW the camera position correctly flatters the horse.. and this is the proper position for taking a good horse photo.
I also think this horse has had an accident of some sort. She has a scar on ehr face, a bunged up left hip and scars above her left hock on the back of the leg. This is not a problem but it may indicate something else (like an accident in a trailer or a hot disposition that results in poor decision making in the field or stall etc.).
Scars are not necessarily a physical problem and accidents are not necessarily an issue either.. but it is something else to think about.
When are you going to look at this horse in person?
Scars may mean she had an accident not of her doing. Coule have evne been in the starting gate. Call and ask questions. She is worth that effort. There is a LOT of class in the look of this mare. I have seen some right fine Hunters that looked like this horse.
IMO if this one proved her self over fences she MIGHT make a good cross on the right Warmblood.. if you were looking to try for a very high level horse at some point. I would love to see this mare's pedigree.