Well, since they met you, they figure they have Peter back.
3 seconds sound clip from the While You Were Sleeping (1995) movie soundboard.
You can hear this line at 00:42:54.774 in the Blu-ray version of the movie.
Quote context
[...]
- Do you want some coffee or tea or something?
- Lucy, there's something you should know.
- What?
- Well, the night you visited Peter, I was outside the door. I know the truth.
- Sorry. You know, you don't have to worry, because I'm gonna tell them everything.
- You remember the day you said you'd never do anything to hurt the family?
- Yeah.
- Well, since they met you, they figure they have Peter back.
- Now, if you tell them the truth, you'll take him away again.
- They need you, Lucy. Just like you need them.
- Now, look, I know you're a good girl. And I know you'll do the right thing.
- Bye.
[...]