Actually a new doc might be a good way to get her diagnosed. Could you find a geriatric doctor and make an appt for her? Maybe you could tell her that maybe she should consider getting a second opinion just to see if she could maybe be taken off of some of the meds. Of course that wouldn't be the reason for her visit but it was always a good way to get my dad in to the doc. And then once we were there, I would meet the doctor just outside the examining room door telling my dad that I needed to use the rest room. It was just beyond the door where I would give the doc all the evidence of strange behaviors (not eating right, not showering/shaving, peeing in his pants, eratic sleep patterns, memory problems, mood swings, getting lost, etc., etc., etc.). It's not so easy to deny when it's documented.
The most important thing is for you to try to keep your cool. Easier said than done, I know. But if your mom senses just a hint of negative feelings from you, she'll pick up on that in a heartbeat and it'll probably send her into a rage.
She sounds so much like my dad.
Live, Love, Laugh.