Karma? Very curious.

Very curious, I've known a mummy that has been talking sh*t about alot of other mommies yet pretending to still befriend them or worst, backstabbing some or to say most of them actually. Why would they do that? Aren't people like them afraid of karma at all? Probably not on themselves but on her own children someday? Aren't we supposed to set an example/role model to our children?