Unbeliever,
I can only speak for what I might do in the situation, based on my feelings, but hopefully this might help at all...
I've never been a JW but am a Christian (married to a DF'd JW); I would think that as long as I felt the mother really had total faith that the org was the "Truth" and wasn't seeming to just hold things out as a lame excuse, I'd feel compelled to be compassionate anyway. Being a Christian, I'd feel additionally compelled to help based on my beliefs, and I'd also want to prove to her that people other than JW's have hearts and actual and practical truth~!