My grandma has a lot of short term memory loss and has experienced some personality changes. Any advice?

Valeriesmith, I believe a lot of clear minded people talk to themselves in the shower, I know I do. It's a great place to vent.

If Grandma seems a bit off, maybe it is time to see if she an urinary tract infection. Such an infection can mimic dementia. Her doctor or even an urgent care facility can run the test. The treatment would be antibiotics. It's worth checking.

I see she is a diabetic. Is she taking her meds like she should? If not, this will cause her, for a better word, become looney.

Your profile says she has Dementia. Maybe its time to have her evaluated to see if she should be alone. Call your parent and tell them there has been a big change. This woman should not be alone anymore. If one of her children can't take her in then one of them needs to make arrangements for an AL or NH. Do not take this upon yourself. I am assuming that you are young with a family of your own. Take care of an Dementia person is like taking care of a toddler who can't learn. Your family comes first.