How do I convince my mother?

My sister who recently passed was my mom's caregiver. She for the most part is pretty alert, but cannot drive, eyesight is poor and hearing is bad. My nephew (her grandson) has lived on my mom's property for years only because his mother my sister also lived there. He is 44, a former drug addict, does not work, collects disability and basically lived off my sister, his mother his entire life. He has two teenage kids, that my sister had legal guardianship over, who also live with my mom. His driving license has been suspended. My mom thinks it's ok for him to drive her to the store, etc. I live an hour away and offer to take her wherever she needs to go. I do take her to her doctor's appts. I want him off her property, and legally I could probably get him evicted as I have POA for my mother. My mom says he does whatever she wants him to do, and feels she is safe with him being there. I am really worried, but she does not want to talk about moving. I am at my wits end. She says he has not asked her for money, (yet) and I am on listed on her bank accounts, so can write checks. I am afraid she will end up giving him money. My sister was his meal ticket and now that she is gone, I worry that Mom will give in and be his meal ticket.