Question about "May" (spoilers)

Okay, so I saw this last night, and it has got to be one of the creepiest movies I have ever seen. It was just wierd, and I felt edgy the entire time. It was great. I do have one question though, for those of you that saw it.

Who’s torso did she use? I originally was thinking it was the punk guy’s, but then that wouldn’t explain why she severed his arm just to reatach it?

I thought it was a great movie. Really twisted and screwed up, not at ALL what my original impression of the film was like at all. I was pleasantly suprised (yet, incredible disturbed).