I see no reason why she could not do running across the countryside and jumping over jumps. There are all kinds of levels of eventing, with and without jumps, even. Like dressage, any horse can do it, but to be competitive is another story.
The mare is well built, for sure. She has a slightly upright shoulder, and a smallish hip, but the angles match the shoulder. She has good bone and good balance of neck to body. She is one of the "Subarus' of horses; can do about anything reasonably well but is neither a sportscar, nor a full size SUV.