If she is five, she is a 'weedy' five year old. Long where she should not be and over all a poor quality horse from a conformation stand point. Regular, correct work to build her up will help her a LOT. Lots of correct trail riding, lots of slow speed trotting over poles, lots of trotting up hills on a loose rein. Build her ring of nmuscles and, like already said, back off the sliding stops and what have you. She may be willing and do it.. but you will ruin her if you do too much.
Now.. that is the conformatin critique. If she is a nice horse to have, good to work around and has a gret disposition and is a horse with 'wiil' then really.. ENJOY her. The best conformed horse can also be the worst dispositioned horse. Disposition is worth a lot over conformation.