Well, she wouldn't have to know. They could sneak up on her and surprise her.
6 seconds sound clip from the Fun and Fancy Free movie soundboard.
You can hear this line at 00:49:02 in the Blu-ray version of the movie.
Quote context
[...]
- Well, Donald may be nuts, but he's got the right idea. Kill the cow.
- Oh, no! The cow was their best friend.
- Well, a friend in need is a friend indeed.
- So what?
- No! If you're gonna kill the cow, I don't wanna hear the rest of the story.
- Well, she wouldn't have to know. They could sneak up on her and surprise her.
- Yeah, that's what we'll do. We'll kill the cow.
- Oh, no, Charlie. You mustn't.
- We'll get a stranglehold on her while she's asleep. And then push her off the cliff.
- Oh, no!
- I ain't a-gonna listen to the story.
[...]