They said Jenny was the 3rd member of the undercover team alongside Gibbs & Mike Franks but other episodes with both Franks & Jenny indicated that the 2 never met before Jenny was Director.
Fire alarms in a hospital are never accompanied by loud klaxons or flashing / strobe lights. The nurse's station would call a code ("red" in the case of possible fire) and state the location of the activated alarm over the speaker system. Hospital staff would then visually confirm before taking action. If an evacuation is needed, instructions would be given. A general alarm like the one in this episode would result in patient panic and possible injury.