After some experimenting, I was able to make the Harasser like me instead, up to 100% friendship and more than 50% lust. However, it doesn't seem like you can change the relationship beyond that. They will still deny requests to hangout or date, you can't ask them to be your friend, fuckbuddy, or master, and despite them making reference to you only being a booty call, they're never available as one in the phone contact.
EDIT: Just saw that there is a new quest in my Hints that has a tutorial for this! Not sure if it was already there, or the new update added it, but yay! Excited to move forward with it!