She remembers! Thank God! She remembers!
This is my theory: I think the medication and drugs Nina has been putting into Olivia's system are there to suppress any memories she has of the orginal timeline including that of her emotional connection to Peter. I think the reason why she has such things despite the change in timeline is because of her unique abilities. I don't know why Nina doesn't want Olivia to remember. Maybe she's a Observer assigned with the task of suppressing a trace of Peter in her. But whatever she has been trying to do to Olivia, I suspect Olivia may not have been taking her meds in a while which allowed her to remember.
Peter doesn't seem happy that Olivia remembers based on the promo of next week's episode. I hope he doesn't do anything stupid.
This episode really gave me the vibe of the good, old days of Fringe when Peter, Olivia, and Walter were working together as a team before the timeline got altered. I was glad to feel it.