Witch with a hairy chin

The witch with a hairy chin was the person who banished the Bandon Banshee. However, shortly after her deed, Gilderoy Lockhart tracked her down, and tricked her into revealing in detail of how she defeated the banshee. After Lockhart got all the information he needed, he cast a Memory Charm on the witch to erase her memory of the meeting and of her actions, and published the book Break with a Banshee with all of the information under his own credentials.