Is this an Obsessive Compulsive Disorder?

I wouldn't call it an OCD disorder. Definatly mental, what were her parents like when she was growing up, there is clearly something here that she is feeling endlessly guilty over things. The only thing I think you as a supportive friend can do is explain that doing this and feeling this way, will make noone love her more than they do (it's the truth...not being mean), that the people who love her, love her. Not her "Please walk on me" sticker on her head. Explain that in the end she will help destroy herself and it's very unhealthy to her well being and to the people around her. Point out the fact that she knows it's unhealthy, when she has kids, does she want her kids learning to let people walk all over them..