I think this Rebecca thing could actually be a good thing. 

So, she tries to kiss him and he rejects her. (Because, come on!, after everything that has happened, we know he won’t cheat on Aaron! (No right now, at least)). After that, he tells Aaron/Aaron sees it. Robert explains him that he and Rebecca had a thing while he was dating Chrissie (because if she tries to kiss him now, she probably did before). 

And that will shock Aaron, because during all the affair, he called Robert “gay”. Even now, that they are boyfriends and they could have talked about these things, they apparently didn’t. I mean, he told Lawrence that Robert cheated on Chrissie because “he was denying himself”. Meaning, he things Robert cheated because he wanted to have sex with men. Now he is with a men. He is not denying himself anymore.

 But the thing is, Robert didn’t cheat only because he was denying himself. He wanted women as much as he wanted men. He still does, that’s who he is. But now he is completely in love, so I really don’t think he would cheat. But talking about that will make Aaron realise that Robert cheated with women too. It wasn’t just about being gay. So they would talk about Robert’s sexuality! I think it’s a good moment for that. We have had some hints about his sexuality lately. The “Chrissie and I actually had a relationship” comment and him referring to gay people as “they”. Maybe this will lead to them actually talking about it.

Maybe Robert calls Rebecca thinking she can help him get back at Chrissie since they apparently arn’t close and maybe he and Rebecca had some sort of thing on the side while he was with Chrissie or even before he was with Chrissie and maybe Rebecca thinks he wants to pick up where they left off when Robert really wants to ‘use’ her/talk to her for info to get back at Chrissie.

I hope it’s something like this/along these lines, i’m not too worried since we know there’s some great Robron scenes coming up after this Rebecca crap.