Tarantino's film editor up until Inglorious Basterds. It's a rule he made everytime the actors fucked up to say hi to her, like saying "sorry we gave you extra work"
For anyone wondering, Sally Menke was the editor so, when there was a blooper the actors or director knew she had to cut, they greeted her. It's like saying, "Hello! Sorry you have this extra work of cutting this footage."