If you truly want an accurate confo analysis, take a photo without tack. Being able to see her wither, back and loin and how they tie together is key.
Looking at this photo, my two biggest areas of concern are her pasterns - fairly long and possibly weak and her neck - some of the under muscling is age and lack of fitness and as previously suggested, dressage work/correct flat work will help. However, her neck ties on high to a fairly upright shoulder, and that is a liability in a jumping horse, and flat work won't fix that.
There's certainly nothing about her that suggests that she couldn't be successful at the lower levels of eventing or jumping; to know if she's capable of going farther, her confo and development at 4 or 5 and her attitude towards her work will be better indicators.