My TB has a roached back. You can sort of see it in this picture... bodonkey1.jpg
He has had no problems and does dressage, show horse events and a little jumping. bodonkey4.jpg bodonkey5.jpg
Roach backed horses can find collection difficult and can have problems with the muscles in there hind end (due to conformation placing stress on their joints, skeleton and muscles in abnormal ways) As long as you help her by asking her to work correctly to make up for her bad posture. Also having someone out to treat her muscles (ie, bowen, equissage, physio etc) will help with the strain and wear & tear on her body. She should be fine. :) Her roach does not look all that bad and you may find if her muscles are released that her roach gets smaller.