I've been saying that for a while but people seem to love her for some reason. Last playthrough after swimming, I ignored her advances and when Johnny said to leave I was like, Yep!, and was out the door. She sent a message the next day saying she's leaving and will never contact me again. Phew, thanks! Lol
I think the OP talk about main quest which are mandatory

But about your post, I have two questions :
- Why even doing her quest line if she that bad? I mean these quests are optional.
- I don't remember Johnny suggesting to leave her, if you play as female (he speak just once when Judy manage to hear him about "toxic waste"). He suggest to leave if you play as male, but she warn V several times during her quests that she's not interested by men... So she doesn't make any "advances" (or I misunderstood what you mean by "advances"
Edit : If you play as female and refuse the romance option when you sit on the bath, maybe Johnny appear afterward (no sure, never tried^^). If so, sorry my bad, ignore my second question
