Any practical ideas for dealing with mom seeing people in her house at night?

One trick I learned was to agree that this wasn't right. I am going to move you to another place but first I will check that no one is there. Then take her to another room that you have 'checked' . Hope it works for you.

Is she taking Ambien?

Have you spoken to her doctor about her hallucinations?

If this is a sudden change in mental status, it could be that she has a urinary tract infection.

But you need to tell her doctor and see advice.