i didn't have too much set in stone, cause i love planning to be a mutual process but the general idea that i had in mind was a long time hook up (cause she doesn't have the emotional capacity for an actual relationship) where they have everyone playing the are they / aren't they game because there are definitely a lot of points where they seem like an actual couple, but according to either of them definitely are not anything of the sort. she's not always the easiest person to get along with, and while they do have a special sort of connection, they're also the best at pushing each others buttons in the worst ways, both say things that they specifically know will target the other. basically it's a typical when they're good they're great but when they're bad it's awful.
like i said we can totally brainstorm and you can toss in any ideas that you have as well!