Fallout 3 Sentinel Lyons Glitch!?

I just got to the GNR place, and Sentinel Lyons and her pals never showed up. I killed off everything (mutants, behemoth, the whole shebang) and now I can't find her. Since I can't find her, I can't get into the citadel. And since I can't get into the citadel, I can't complete the main quest. What am I supposed to do?