He's gotta be talking about her new mom from Namgung. Or, I also had a thought, that maybe she was abducted shortly after birth. And Seol's memories from when she was a baby was with her real mom (not the Myo mother), and I'm thinking her real father is the hero from the beast clan ( I think that was what he was called). The two things they threw in about how he's actually a cat shifter AND his special ability is being able to communicate with animals matches up with Seol. So that's the hypothesis I'm going with fur now. (=・ω・=)

A mother's love? That woman who treats her like garbage?! I think it means the one that loves her dearly, is her real mother.