I did a more passive-aggressive version of this, basically.<quoted text>"Dude, really? It's cool I 'get' it, but you know, D was already invited and un-inviting someone isn't cool -even though he will totally understand and be cool with it too- but I feel like I would be ditching him, on a weekend night, so I'm going to have to bail on Friday night, and get together with you guys for a girls' night/day later. Sorry..."
But, yanno, nicely, and no sarcasm on the "sorry" part.
In other news, just now I went against everyone's advice for the first time and called Jasper. Got voicemail, left a message saying happy birthday and I hope he's doing well. Why did I choose today for this? No idea.