What should I do about my mom?

My brother went to go visit my mom and found drugs in her apartment.. he threw it away that day. Our mom confronted him and got upset explaining why she started using it. We told gave her an ultimatum us or drugs she basically said she’s her own person and she can do what she’s wants. So she’s not choosing on or the other but leaving the choice up to us because she said shes going to do what she wants. My brother and i have very little family. Her and an aunt is all we have so we don’t want to cut her off bc we don’t want to be so alone in life and obviously love her, but at the same time drug use like this is gross.. i also have a 3yo she adores but i can’t let her go over there knowing this. I can’t articulate an exact reason why i don’t like her using drugs or why it’s bad.. or why i don’t want my daughter to have anything to do with her now. I’m lost help

Is it like hard drugs or weed? If hard drugs… i wouldn’t completely cut her off, but I would limit how much you see her. If she wants to see your daughter, meet at a park or for lunch. I wouldn’t let her spend the night. It might sound harsh but too many things can happen.