Been there, done that. My first love developed bipolar disorder after a horribly stressful life experience (it happens that way sometimes, it's latent and then something triggers it). He was the sweetest guy when we first dated, kind, thoughtful, considerate, classy. When he got sick, it was like Jekyll and Hyde. In the course of a few months he caused serious damage to his parents house, crashed two cars, got arrested and nearly hurt me several times. His parents ended up having him committed then hospitalized to get him stable.
I have a very, very good friend who is a psychotic bipolar and she's what I would consider "brittle" in that she has huge problems when her meds get changed, frequently has to be hospitalized. Unfortunately she also has miserable side effects with a lot of meds but she doesn't want to be sick and does what has to be done.
Like I said, it can ruin the person's life and the lives of everyone around them and if your GF is in denial that makes things 1000x worse. All the other health problems you listed are only compounding things.