I don't think it poses any risk. It does appear to be very lightweight and flimsy so even if the horse goes crashing through it I think she would be perfectly fine. It's also low enough that she isn't likely to land wrong or have any major problems.
I will however agree that it is generally much better when formally jumping to have a set of standards and a ground pole under the jump which will make it much more clear for the horse.
As far as the pictures go, it is hard to get a real idea for her conformation as none of them are very direct standstill images. She does not appear very overweight in any of the pictures that you showed us, so I wouldn't worry about that too much. She might do well with a little more muscling along her topline.