Need help with guardianship

Hello mommies. Sadly I’m in a pickle, my sister is an unfit mother gets to relationship, drugs disappears and leave my nephew tj my mother and will not come home. She will sleep in and not feed him and not comes back home and when she does it’s for money. I need help to see what are the steps or a good attorney in Los Angeles CA. What can I do to get guardianship of him. This is an ongoing cycle my nephew deserves better. Is there an emergency guardian I can file. She doesn’t want to be a mother but won’t let him go since she’s getting assistance that’s why she’ll keep him I know it. She doesn’t care, so many years of taking intervention her going into rehab a few times she loves being in relationship she needs a man to be happy and that’s not happiness. the lifestyle she’s Living is it healthy for her and her son help. This is not right what can we do