The short answer to your question is this: nothing, though it sure looks like something. Arthur Miller's The Crucible is set in Salem at the time of the infamous witch trials, and everyone knows witchcraft is a serious--and punishable--offense. When the play opens, we are concerned because ten-year-old Betty Parris is lying on her bed, inert, and everyone who is close to her is worried because she will not wake up.
Her father, Reverend Parris, has sent for a nearby expert (Reverend Hale) on matters of witchcraft. The Putnams come to the Parris home because their daughter is suffering the same malady; they, too, are convinced that witchcraft is to blame. Rebecca Nurse comes and is compassionate, but she believes this is just a "silly season," which all children have occasionally.
Abigail Williams and Parris (her uncle) talk, and we begin to learn the truth. The girls were dancing in the forest last night. When John Proctor comes to the house, Abigail tells him the truth. Betty is acting like this because she does not want to get in trouble for being in the forest last night.
Abigail smacks Betty around and threatens Betty and the other girls not to tell the truth about last night; they are just to say they were dancing. Betty suddenly comes out of her stupor.
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!
Betty, collapsing on the bed: Mama, Mama! She dissolves into sobs.
The only thing wrong with Betty is that she did something she should not have done, and now she is trying to avoid getting punished for it.