I wonder if it's her obsession with the Joker that seems romantic to them. Like, fatties obsess over guys, and never/rarely get them. When they do, they're treated like garbage (bc they are). HQ & Joker's relationship is similar to a fat's "relationship". Probably makes them feel badass too, because she's a "bad" girl. I suspect thin girls do it to make the pigs REEEEEEEEE with jealousy :)