I think that Jen felt that Jack hadn’t changed as he claimed. Jen thought that they had gotten past all the games that Jack had played and they now had a truth pact so to speak. That coupled with jack assuming they were back together just really ticked her off. I think she feels that he really needs to step it up befor she can commit to him. At least she is sticking to the no sex condition. I can understand her being angry cause she felt he was deceiving her yet again. Also she does have feelings for Dan, but in the end, I think she will return to Jack.