She's done trying to court Darling like a human girl. Time to go full rape-snek.

Her mother will certainly approve.

Also, the reason we don't really know anything substantial about Miia's father is that he had an intense fear of snakes so strong that the sex skills of lamias just weren't enough to get him to stay.
Heck, we know more about Centorea's and Mero's fathers than we do Miia's. They may be just as absent, but still are given more character by the words and actions of the mothers. Fear of snakes is all we've got for Miia's, and even that's only mentioned in a special chapter, not by her mother.