my mom attacks me viciously with insults. She's always had a touch of it in her but now it's non stop. sometimes she likes to act like she's disguising it but she know she's not. When I call her out on it I get different reactions. This behavior is getting out of control.
Are you living in her house? I see that you are caring for your grandmother as well. Do the three of you live together?
A little more detail will help us respond more specifically.
At the least, she is probably suffering from anxiety and depression. In men, depression is often expressed as anger, not sadness. That might be what she is doing. Whatever you do, don't tell her the medicine is for mental problems. Tell her it's a 3rd generation pain medication, or for her blood pressure.
Of course you can ask at the senior center! Probably everyone on the staff has experience with dementia, and can offer their considered opinion.
It really sounds like she needs a thorough evaluation. The behaviors you describe could be symptoms of dementia, but not necessarily so. How is her memory? How is she at making decisions?
Is this attacking you a new behavior? Or has it been going on since you moved in?
On the face of it, if she has no impairments she shouldn't need a caregiver. If she resents you the best course of action might be to move out and just visit her regularly. But I suspect that if you consider yourself a caregiver there really is more going on with Gram than nasty comments to you.