Well, one of them was kind enough to try to kick her in the back of the head instead of, say, stabbing her, so I don't know if they're 'killers' per se..
Mookieisms/superhero genre conventions aside, she absolutely could just dispatch them. She might not be able to do so without risking unacceptable collateral damage to the people she's trying to save/room/building/planet; there's a fairly large discrepancy in the amount of power and finesse applied between 'blow up a spaceship' and 'kill/disable a handful of human-sized mobile targets.' Doing one does not necessarily imply being able to do the other.