About guardianship? Advise please?

My ( friend ) more of an acquittance, and her husband are pretty unfit parents. He has 1 child from a previous marriage taken away. She has 3 kids. 1 she wants to sign over to her grandma, I have 1 for the night and she has the baby. They steal everyday with her 2 with her. Today she got caught. She called me and had me come down. They didn't arrest them? Just a petty theft ticket. They do drugs, have 3 sums...They don't feed her right. I remember being on the phone with her and she said " Here is a bag of Cheerios, " that was for lunch. I had them come over here tonight and told them I wanted her to stay with our family for awhile. Her husband has psychotic issues and got mad. He said " It er-ks me that you are saying we cannot take care of her. " I said I am giving you guys time to get things in order. They seem to love her, They just don't take care of her well. She is living a pretty rough life. I talked to my husband and we want to have guardianship. The dad is pretty hardheaded. He said they will be back for her in the morning. I want to tread lightly, but put across that we want her. Her mother said, " With you I know she will be in good hands. " Its the dad thats ruining everything. We feel so sorry for her and know that we can provide her a whole different life. Any advise would be well appreciated