I kind of hope Sophie’s gotten married in the two years since we’ve last seen her. It could lead to the reveal that part of her motivation for sleeping with Dan was a fight with one of the fathers of her children (and that she blamed Amy for not being supportive enough) but since blowing things up they tried to create a more conventional relationship and it makes them miserable. Dan can feel how really impersonal it was for Sophie and to emphasize how big an impact Amy leaving had on her sister.
Here’s the thing – would Dan CARE that it was impersonal for Sophie?
Admittedly, Sophie’s been so loosely written (as is inevitable for a character with only a few short appearances), that the show can basically do what they want with her. They could have her regret driving Amy away for so long, or they could have her basking in the warm glow of knowing that Amy’s life is just as messed up as hers is – either would be in character at this point.
But if Dan realised that say Sophie was in a sloppy or vengeful mood because of some other man, and that’s why she slept with him, I really don’t think it would bother him all that much. I suspect that, for Dan, Sophie’s feelings are only important insofar as they make Amy pissed off with him (which may be why, by his standards, he let her down fairly gently with the “what happens in Vegas stays in Vegas” line – he was probably nicer to Sophie when dumping her than he was to Amy the first time round).
Now, if he found out that Sophie was never actually attracted to him, and was thinking of someone else the entire time…maybe he’d be annoyed by that, but not for very long. His actual feelings about Sophie seem to range somewhere between indifference and actual dislike (Reid Scott didn’t have much chemistry with the actress either, which helps the story, I think, in this instance) so I think he’d brush off any wound to his ego fairly easily.
I guess it depends on who the showrunners really want to torture. If it’s Amy, Sophie will have married and basically got her life together since the last time we saw her, casting Amy as the Prodigal Daughter – but if it’s Dan, Sophie will still be a fuck-up and will continue to try and insert herself between him and Amy. That would mean Dan would have to deal with TWO women he’s screwed over, neither of whom he can get away from, and neither of whom, realistically, he can piss off too much. It would be fun, in other words.
As for Sophie being miserable, I think that’s a given. A happy person wouldn’t attempt to tear their sibling down the way she does with Amy – don’t get me wrong, it’s perfectly normal to be aggravated by a sibling, but to go after their long-time love interest the way Sophie did…
We haven’t seen any of Amy’s family since they found out about Dan and Sophie sleeping together, but I can’t imagine her parents were particularly happy about it. In fact, it seems likely to me that Amy’s parents would be extremely worried about her – they know she had some kind of feelings for Dan, they probably know she’s been professionally frustrated, they definitely know her break-up with Buddy was humiliating in the extreme… and now she turns up pregnant? And potentially tied to a man who is, at best, wildly untrustworthy. (Not to mention their own experience of Sophie being a single mother).
All of which will no doubt make Sophie WORSE. She’s never liked it when Amy has attention paid to her – I can’t imagine she’ll like it more when Amy usurps her position as the successful (ie reproductive) child and starts sucking up more of their parents’ love and attention.
It’s hard to blame Amy’s Dad for loathing Dan so much, I have to say.