God parents

My good friends daughter is my god daughter and I love her like my own. And I love my friend of course. Now she's not the most reliable or responsible person but she pretty much volunteered herself to be my son's god mom. She's like a sister to me. I've known her forever. The only problem is if anything ever happened to me I can't say I'd leave my son with her long term. She still likes to party and pawn her own kid off to do so. Idk how to gently tell her no. She's extremely sensitive and I don't want to start a huge fight between us..