Becky Murtaugh is the second daughter of Jimmy and isn't seen much. She has only two lines in the whole movie
Becky Murtaugh
. The first is an exclaimation of "Ooh!" when her brother Daniel reads something important. The second is "Not cool Dad," when she dives into the lake after her younger brother Elliot.
Becky can also sing very well. It is most likely that she (and the other Murtaughs) plays an instrument, seeing as Elliot plays the timpani at his school's orchestra. It is also likely that she's an overarchiever like her siblings.
Becky Murtaugh is played by Melanie Tonello.