Is it safe for my fully vaccinated 85 year old mom to be around her son who is not vaccinated? he comes into the house and sits at the kitchen table about a foot from her, sometimes with a mask on sometimes not?

Safety is relative. Nothing in life is guaranteed except "death and taxes", as the saying goes. Thus, in this deadly pandemic, every eligible person should be vaccinated unless there is a major risk to the person receiving the vaccine. If an elderly person gets sick, bad things can happen. Most people don't want to risk losing Mom or Grandma. In the US, 600,000 people have died of COVID so far.