I'll give you a hint cuz I just figured it out. You have to perform a certain pose on the pink-haired delivery girl for a lengthy amount of time until she says she doesn't want to come back again. Hope this helps.
Might be a dumb question, but with melanie i only get the handjob animation. I might have a faulty version of the game. How do you progress to more than a handjob?'
Edit: just as i said it, i got it fixed. Much love yo you guys
