First, she argued with her boyfriend about his being indecisive and failing to "take charge" of any situations. He stormed out, knocking against the gun so it pointed at her. The second time, she tried to throw some of the goo on him, and in the process bumped against the gun, causing it to shoot Jenny and make her grow again, so Jenny's girlfriend ran in and pushed her into the beam.
That clear it up? If I can figure out how, I might vidcap the entire DVD and post it. Be warned, the acting's even worse than this stuff makes it look.