The only thing is, we already know the mother lived in NYC, was at the Saint Patrick's day party that Barney was at with Ted, and was roommates of some random one of the girlfriends who I can't even think of right now.  So how could Barney's sister have lived in NYC during that time and not have met Ted through…

I really don't even care, I hope they retcon the shit out of it and just make Victoria the mom.  Ok maybe not retcon, but just find some way clever way that "meeting her" at Barney's wedding has a different meaning or something.

SPOILER FROM COMIC: