Getting the Hellhound to grow a dick?

[CourtOfTheGrayWaves]

Like how many encounters does it take ta unlock the option?

 

[Tarnakus]

You need her at Wayfort -> which means getting her pregnant first and waiting for her to deliver. Then she becomes non-hostile. With upgraded Wayfort she visits and asks to stay. Then you or companion that needs to be futa and that unlocks talk scene and giving her blue eggs.
I'm not aware if there is other way around.