I think one of the hardest things to learn in life is that you can’t control other people. You can tell her whatever you want but you can’t make her get a job and you can’t make her go. You CAN, however, control your actions. “I’m not comfortable with the way you talk to my father. If you continue to treat him (in this specific way) I’m going to limit our visits to (whatever makes sense for you: holidays, once a month, etc.)” Same thing with your father. If he’s really bothered by her actions or inactions, he can set boundaries around how much he financially supports her. I’d also encourage you to talk to her doctor. Is she in therapy in addition to the meds? That would likely be helpful. It also might be helpful for you to talk to a therapist regarding how to manage your relationship with her.
In my personal opinion just from reading this. If your mom having no job and no income is hurting your family, I think you guys need to sit down with her and make her realize what she is doing, is doing more harm than good. In all honesty you can't help someone who doesn't really want it.