Watched the last two episodes last night. I'm in love with this series. I really do.
While I suspected right when Olivia approached the unconscious Bell that it was alternate-Olivia (apparently fans nicknamed her "Bolivia") and I was certain of it when she got to "her" apartment and knew exactly where to find the key after the two Olivias' conversation, and looked at the interior in owe -- it was still a great ending. I assume Peter, when regains his senses after returning to what he now calls home, will see she's not this universe's Olivia, if he looks right into her eyes. And I bet that despite her training she won't be able to hide her true nature, which is quite different then Olivia's. Oh, and their kiss. She won't know about that (unless she had time to watch video footage from the apartment, and they surely had cameras in there).
Anyway, I'll probably have an "OtLB" written about it in preparation for Season 3.