The thing with "Jenny Burton" was explained in the Sarah's last flashback in "Versus the Cougars". When Graham is recruiting "Jenny" for the CIA, he lists off that name as well as a bunch of other aliases she used in different locations as she lived on the run with her dad. Sarah interrupted him before he could get to her birth name.
Sarah never told Chuck that Jenny was her real name. He was just listening in when her old classmate called her "Jenny" and assumed that that was her real name. Sarah just let him continue assuming that - though I assume that once Chuck met Sarah's dad, it became clear that the assumption was a false one.
Phyllis, every fan I know is just plain relieved that the show put Chuck and Sarah together instead of extending the will-they-won't-they nonsense. They make a cute couple and the show isn't suffering for it. I just want them to actually do a mission with Casey again as a team. It's been ages.
ETA: Here's Graham's little speech to the teenaged Sarah in "Cougars":
"The question is, who are you? In San Diego you go by Jenny Burton, in Wisconsin it's Katie O'Connell, Cleveland it's Rebbecca Frenkel. Funny thing is, when I looked at your birth certificate..."
Then he got interrupted by Sarah.
Updated On: 5/15/10 at 12:52 AM