The ridge comes from not stuffing enough nipple (especially the lower part) far enough in to her mouth. It does improve as mouths get bigger and nipples get softer - but in the meantime, make sure she has as much nipple as you can get in there.
Is a lactation day stay an option for you?? It sounds as though the problems can be different in different feeds, so evaluation of a few feeds might help to really work out what is going on.