Man I really need to get to work on Sparkler because SHE WILL BE THAT FRIEND. She will drag Della kicking and screaming into Skittles if she has to, and she put a shot in front of her and stare her down until she drinks it. And then she will be the wingmanniest wingman there ever was, and she will get Della to snog a fit girl. And Della will LIKE IT.
But as far as the kid I actually have accepted already goes, I think Fred and Della would be casual Extremist acquaintances, and they could get friendly. Fred's too quiet to really be that friend she needs, but he'd be a good stepping stone to Sparkler, I think. Get her a little more ready for her.