Mary, in an attempt at kindness and placation towards her employer, Elizabeth Proctor, sews her a little poppet, or doll, during court one day. Elizabeth and John were disapproving of Mary's trips to town, and of her participation in the courts, and had even forbidden that she go. So, to ease the strained relationships, Mary sews Elizabeth a little doll, trying to show her kindness, and to try to appease Elizabeth's anger about her having disobeyed orders to go to court. Elizabeth is a bit baffled by the gift of the poppet, but accepts it.
Later, unfortunately, the poppet plays an integral role in Elizabeth's arrests as a witch. Abby saw Mary stick a needle in the doll's belly "for safekeeping," as Mary said, and takes the opportunity to devise a scheme to get Elizabeth arrested. At dinner that night, Abby falls down to the ground screaming and pulls a bloody needle out of her belly. She claims that Elizabeth's "familiar spirit" shoved it in, in some sort of voodoo doll curse. That "evidence" is what leads to Elizabeth's arrest, as the doll is found, at her house, with the needle in the belly. Despite Mary claiming the doll was hers and that Abby saw her put the needle there, they arrest Elizabeth and take her away.
The irony, which is an occurrence that is the opposite of what you might expect, lies in the fact that the very doll that Mary gave Elizabeth in an act of kindness, is the doll that ends up getting Elizabeth arrested. The poppet, a peace offereing from Mary, turns out to be the harbringer of horrible news, and the tearing apart of Elizabeth's family. I hope that helps; good luck!
She gave her a poppet (a doll) that she had made that day in court. The poppet had a needle stuck in it still (for safekeeping), which Abigail used to accuse Elizabeth Proctor of witchcraft.