I think so too. Marco is going to think about Star a lo and their incredible adventures togethert and no matter his true feelings he's going to want to go after Star. I think Jackie will notice this and they will both agree that Marco has to rethink some parts of his life and they seperate on friendly terms. They'd still go skateboarding from time to time.
I'd imagine she felt kind of guilty when Star confessed at the finale. You know since, actual, canon Jackie is a really nice girl compared to what all the retarded autists here make her out to be to fuel their perverted fantasies. Once again it's really easy to project unto Jackie based on desires alone because she hasn't been anything else character-wise BUT Marco's girlfriend. There's a lot of space to imagine things into.
She actually seemed to get along well with Star in Just Friends. And she along with Marco believed that that's why Star was there. To be a friend rockin out to some Love Sentence with them. I think that initially Star beleived the same thing. But in the finale we got this:>I thought if I just pretended the feelings weren't there they'd go away.
So this whole fiasco wasn't really anyone's fault but the feels. Star WANTED to remain friends with Marco. (Both of them remembered the things they did together very fondly.) This is why she kept it a secret so long, she was trying to regress these feelings. But she just couldn't help feeling the way she did and it seems like there's no going back. (possibly Blood Moon Pact in the works?)
Anyway Jackie is not a cunt. I'd imagine that she would think that Star had some similar otherwordly, loony bf somewhere on her home planet and they were really all just friends. But now that she knows what's up it's a little more awkward to her because she wouldn't've wanted to make Star feel bad on any level. She really thought of her as a friend. It wasn't anger on her face but genuine shock.