Continuity mistake: In the side of the story when Lois takes the boys, Malcolm has some kiddy bumpers put in to help him bowl. In the next scene when Reese is about to tell Beth the joke, you can see the lane which Malcolm was just at but there are no bumpers in the gutters. Then later when Malcolm stands up to Lois they are back in the gutters.
Other mistake: When Reese lights the fuse for the fireworks, Malcolm says the fuse is timed for 20 seconds. When the diving board collapses on Reese, it is around 30 seconds after the fuse is lit before the fireworks start.
Factual error: It's very very unlikely that police would chase all those women through town (even take helicopters to arrest them) just for making noise on someone's property for couple of minutes.
Answer: It is made up - although it is implied she is Croatian, she never mentions it herself.