I feel like in an alternative universe somewhere Sue and Amy get manicures together on the weekend and bitch about everyone at the office (including dan- especially dan)
To be honest, I think something like that is at least implied by the show. Maybe not to quite the extent you’ve described, but I think it’s clear Sue and Amy are friendly.
In 2.06 Sue sure knew a LOT of information about Ed right off the top of her head – she certainly rattled it all off to Dan with surprising speed. (In the Behind the Scenes for this I worked on the assumption that Sue at least knew Dan was probably going to try to sleep with Amy again, even if Amy hadn’t realised that).
She also notices – BEFORE Dan – that Amy is upset in 4.10, and she does that just from seeing her on air. Not only that, she goes with Amy to Selina’s suite, even though she could easily have stayed home. But she knew Amy needed back-up.
She and Amy also have an interesting little chat over the phone in the Finland episode – Amy talks about her period (which is why, dashing the hopes of dozens of fic writers, a Finland hook-up is impossible. Though I remain convinced 6.09 was the first time they’d slept together in the show – their dynamic doesn’t make sense if they’d given in earlier).
The one thing that pushes against this is…I cannot believe Sue would have ALLOWED Amy to see Dan again in 6.05, so soon after the break-up with Buddy. She really wasn’t in an emotional state to see him, and I think even DAN knew that to at least some extent. That he didn’t make even one joke about Buddy exposing himself, even when Gary told his story, points to that. Gary showing up prevented things from escalating, but you have to wonder what Dan was hoping to get out of that evening.
Of course, Amy was in New York and Sue was in DC, so Sue may not have been able to administer the required bitch-slap of common sense in time. But I feel like any friend of Amy’s who knew the full situation (though Sophie may be the only person that applies to, who knows) would have wanted to keep Dan away from her while she was still visibly depressed over everything with Buddy. Dan isn’t someone who people would expect to handle emotional vulnerability in a remotely sensitive way.
Sadly, Sufe Bradshaw’s health issues may prevent us ever seeing additional scenes between Sue and Amy, though obviously I hope that’s not the case. With luck, we’ll see her again in season 7. (Maybe she and Amy can bond over loathing Candi Caruso).