My friend might have multiple personality disorder or might be possessed. TLDR: is there a way to get rid of a personality or spirit that latched on to a person?

My friend apears to have multiple personality disorder. She clearly has multiple personalities that act very differntly, talk in different ways and call themselves different names. Ive met some of them and they seem to believe that they are souls of people that are dead and have latched on to them. Idk about all that since im a sceptical person but whatever. Point is she has developed a personality that seems to believe she is a nymphomaniac and as a result she is very sexually active. Ive talked to one of her personalities which seems to be her "guardian" ill refer to her as "G" from now on. G seems to think that there is a way to get rid of "N" (nymphomaniac). Also forgot to mention that she has been medically diagnosed with bipolar personality disorder and is attending therapy regularly. I also really doubt she would be faking it because of the sheer amount of fucking dedication she would have to go through to do so. I mean like creating completely different character arcs for each one of her (to my knowledge) 6 drastically different personalities. Idk it might be possible that she really is possessed or some shit but if there's even a slight chance that some weird ritual or some shit might work than ill fucking take it. I am asking for serious answers as i am worried that N really might get my friend hurt. If you have any questions that might help than ask away, ill answer as best as i can. I am asking for honest advice on what I should do in this situation. Is there really a way to get rid of multiple personality disorder or a single personality or a latched on spirit or some shit? Or should she just seek more intensive therapy/treatment?