What is incumbent upon a girl afflicted with obsessive-compulsive disorder (OCD) regarding purification and prayer, who has made numerous vows and oaths that she has broken due to interrupting and repeating prayers?

The cure for obsessive thoughts (waswas) is to ignore them and not pay them any attention. If the oaths and vows were made or broken under the influence of obsessive thoughts, then nothing is incumbent upon you, because you are in a state akin to being coerced. However, if the action was not under the influence of obsessive thoughts, then you must offer expiation for any oaths you are certain you broke and any vows you did not fulfill. As for anything you are doubtful about, it is not incumbent upon you.