well, its the one with the car chase, when Babbyface Nelson is being chaced by the cops and he says "cows, I hate cows worse than coppers, blam blam blam blam" I think that part is funny myself, because you can see they just stuck those little pyrotecnic things on the cows so it looked like they were shot
but I would put the dvd in a dvd player and find out what chapter thats in, you dont need to remove the file, just tell her to skip ahead to the next chapter when it comes to that part
or I think the files are organized in chapters for the computer as well, so all you have to do is once you find out what chapter the chace(and theus the cow shooting) is you deleate it, now I bet those files say somehting like "when file number ** ends begin file number **" if I am right, I have no idea if I am, but if I am, than all you would have to do is rename the subsequent files the name of the file before it.
those are all just ideas, no guartee they are the truth
of corse you could just tell your sister to buck up and than show her that message at the end of the movie that sais "no animals were harmed in the making of this film" that should chear her up (of corse I dont know your sister lol)