Rather than trying to nail down the diagnosis, this might be a time for you to consider what is happening in the relationship for you. Your email says your girlfriend has schizophrenia, or bipolar, or maybe schizoaffective, or has DID (Dissociative Identity Disorder). She also and has a therapist and hasn’t discussed being sexually abused, and doesn’t like talking to therapists. My question is if you want to take this work on of managing your girlfriend’s recovery? Is this the kind of person who can be in a relationship right now? It sounds like you may not be involved with someone who has the capacity to be in a committed relationship right now.
Dissociative Identity Disorder (DID) is something diagnosed by a mental health professional, typically a clinical psychologist or psychiatrist. There are several symptoms that underlie DID and the primary one is that it disrupts the person’s identity as other “personalities” or personality states manifest. These often include different voices, and in some cultures can even be identified during these states as being possessed.
If this is what your girlfriend does have this will require significant therapy to get under control. I would encourage you to ask your girlfriend to visit her therapist with her. This gives you a chance to talk about the relationship in a safe place with her therapist.
This gives you a chance to pass-on your points of view to her therapist, to ask how you can help, and to discuss if this is the right time for a personal relationship with her.