Betty reveals that the girls had actually participated in witchcraft. Abigail is *very* worried that she will spread her knowledge to others and get the girls in serious trouble.
In this exchange, Betty tells Abigail what she saw, and Abigail responds swiftly and forcefully:
Betty: You drank blood, Abby! You didn't tell him that!
Abigail: Betty, you never say that again! You will never--
Betty: You did, you did! You drank a charm to kill John Proctor's wife! You drank a charm to kill Goody Proctor!
Abigail (smashes her across the face): Shut it! Now shut it!
Abigail continues with her threats until Betty is sufficiently terrified into silence.