you answered your own question:
- She should, because they met in the past while Jin was traveling through time. Jin practically saves Rousseau's life when he doesn't let her go down the hole to the smoke monster
I would say that she does not for two reasons: 1 - She has been alone for a while and could be a little 'off'. 2 - Jin has not yet time traveled and, because of that, Rousseau has yet to meet him. Her experience reflects that of the original timeline (no Jin found on the island). This goes along with Faraday's theory. Like Ben was never shot as a child until Said traveled back in time.
I kind of disagree, Rousseau should recognize Jin, following Faraday's theory that the future cannot be changed (his theory that it CAN change fails when he is killed by his own mother, and the mother knew it all along while she was raising him). Besides, if Jin didn't help Rousseau, she should have died when they were attacked by the monster
Think about Back to the Future part 2, Before Jin travels in the past, Rousseau has not seen him in the past because it hasn't happened yet. Anything changed on Timeline A season 1-4 isn't resulted by anything happened by the accurances in season 5. At season 5 timeline B starts. also know as (sideways) As for above stated Faraday theory, Eloise leaves the island allowing possible time travel as well. So she quite possibly knew it from that. Hint and point When Ben left the island he made it a point to ask what year it was.