I think it’s Robin, because Ted didn’t look at all surprised when told that the bride wanted to see him. Someone above said they looked surprised but I didn’t get that at all. In fact, it was pretty much like an assumed thing. Must be Robin.
Also the fact that Lily is hanging out with the bride before the wedding points toward it being Robin. She wouldn’t have become close enough to Nora before the wedding date to warrant an invite to be a bridesmaid or matron of honor.
I do like the theory of Ted’s wife being Barney’s half-sister. The show tends to not have throw away lines, and the dialogue about her being in college in NYC is too specific for it to not be significant.
I don’t think the fact that the bride asked to see Ted means that it’s Robin.
- Lily looked surprised. I don’t think she’d make that look if it was Robin 2) Robin is friends with Nora, so she might be in there with the bride. There could be any number of reasons the writers could come up with for Nora asking to see Ted… and 3) Who’s to say Nora and Ted don’t become relatively close this season? They seem to have a lot more in common with each other than Barney and Nora
That scene just wreaks of a distraction to me 
I’m willing to give the benefit of the doubt, but the obvious answer is, the wife is Nora and Barney has second thoughts because he loves Robin, and will pull a misses "robin"son.
:: pulls knife from chest ::
