I have an issue that I hope someone can help with. My granny has been her sister's POA for a while now & I had to move in with my granny in 2016 bc of the onset of dementia/Alzheimer's. My mom & uncle told her it was either that or she would have to go to nursing home. At this point I'm my granny's POA but doesn't that cancel out any POA she may of been since she isn't able to tend to it now. I thought her sister would have had it changed by now bc she knew she had dementia but I'm getting things addressed to my granny as POA. Please help.
Meanwhile, all mail you are receiving, should be returned by you, as POA for your Grandmother, to the sender with a letter (print lots of them) explaining you are POA for your Grandmother, and that she is incapable as fulfilling any duties of POA for anyone now and in future. This will lead the entities to contact the sister. If this sister is currently herself already demented (My guess as your Granny was already acting for her, apparently) then the family will have to intervene to get guardianship, which will negate any former POAs she may have done.
If there IS no family for Granny's sister (my guess, as she made her sister POA) then there is a larger problem if this sister already suffers from dementia or is in care. This would be a problem to take to an elder law attorney or Adult Protective so that they can arrange State guardianship and appointment of a fiduciary for Granny's sister.
You said, "At this point I'm my granny's POA..." FYI you are not your great aunt's PoA on behalf of your granny unless you were named as an alternate in your great aunt's document. Only your great aunt had the authority to make this change.
Best to find the document and see for yourself.