At the very least, she shouldn't be jumping him. Can you imagine the extra stress it probably puts on him? A horse I had many years ago had stress fractures (from before I bought him) in his front legs just from his own weight (big ole draft cross) and wasn't allowed to jump.  And I love how she's like "no one else will let me ride so I just bought my own horse." Yeah, maybe everyone else doesn't want their horses to suffer trauma from an overweight rider and break down in a few years. Uuuugh.