I'd assume part one. I mean (**SPOILER ALERT!!**) the cut off for part on is when they are taken to Malfoy Mannor. The silver doe (and the locket scene, which we know is in the movie) came before that.
yeah p.1. i guess the cut off for the film will be dobby and malfoy manor as it seems like a dramatic ending for the film plus a general halfway for the book??