As soon as the man rolls away from her, Terezi rolls the other way, scrambling to her feet. Her weapon is a dozen feet away from her, and she only has a split second to decide whether to go for it or not.

There's no chance in hell for her to disarm that bomb now. The best course of action she could take is to get away and inform another team to either engage or evacuate the area. But she is in an active warzone. Trying to navigate her way back to the rebel camp without a weapon would be tricky at best. Most likely, she would run into another situation like this, except without a means to defend herself.

She makes a run for her staff, lying a few feet from the side of the building that she found the bomb nestled against. She only needs to get close enough to stoop and grab the weapon, then she can beat a hasty retreat.