How do I tell my friend her house is inhabitable?

My friend has a six year old. The house is a complete mess. The bathroom has mold and mildew. There's cat vomit on the floor, along with the litter from the cat box. Her clothes are piled high, as well as her sons. There's an old, greasy stove in the living room, etc. I helped her clean her trailer before and dishes were piled up with black mold (she wanted to wash them and save them!). She's stressed, but escapes by calling me and another friend; or goes to a family members house. She even ignores comments my friends and I make. I worry that it's going to cause health problems for her and her son. Also, it's adding to her stress level tremendously. I just don't know how to tell her without sounding like a B. After already helping her once before, I really don't think I should this time. Any suggestions?