They're both orbiting Starco and will be the rejects, they could easily bond over that. Or indeed Tom could get angry at learning that Marco is hitting on Star after all and would go after Marco's "girlfriend" in retaliation.
Also Tom, despite being the demon prince of Hell or whatever is canonically trying to find himself - according to Nefcy his dad is an anger demon so it's his blood heritage but he's trying to get over that and has a vulnerability beneath, he likes trashy bands like Love Sentence, playing videogames, ping pong, tries to dress rebelliously, admires Star because she does whatever she likes. He's trying to buck the expectations and hopes someone would like him for him, see through the infernal prince of demonic darkness facade.
So Jackie, who's incredibly laid back, chill, good natured and just down to hang out, could be a great match. I can see her being sort of weirded out at first but just going "whatever" and getting with Tom simply because she finds she likes him and his company and his casual alpha confidence and romantic gestures, and not because ooh demon prince of darkness and hellfire and magical necromancy powers ooh. She's so incredibly cool and easygoing I can see she'd have a calming effect on his temper, too.
Also it'd just be fresh and interesting imo. Kinda unexpected but still working, strangely. A bit Beauty and the Beast, a bit 80's teen movie with the hot popular sporty girl getting with the punk rock angsty rebel boy.
The more I think about this the more I like it. I never used to pay attention to Jackie before Naysaya, but she could have potential.