Why does Harriet change her identity?

I've found two conflicting pieces of evidence and a discrepancy between the shooting script and the transcript of the movie:

Shooting script:

Rose: (mostly to herself; slurring most words) Charlie, did you like your note? I thought it was pretty accurate. I did all the husbands' notes. I can forge anyone's handwriting, I can write in anyone's style. See, I'm an artist. Harriet isn't an artist. Sure she could get a husband, but she could never have done this. And you know what I'm most proud of?

Charlie: What's that, Rose?

Rose: Harriet never knew. She thought they all just left her. I protected her. She's my sister.

^{From: imsdb.com}

But, from the transcript and not the shooting script (these are the lines that I remember):

Charlie: Rose tried to kill me.

Harriet: What?

Rose: Shut up! I wrote this note! You're not to be here when... ...this note has been placed on the desk!

^{From: script-o-rama}

I infer from the transcript version that Rose is chastising Harriet for being around when she's about to murder Charlie, and that Harriet should have been aware that she was supposed to stay clear from the scene from having either known about or witnessing the prior murders. Rose couldn't have possibly been telling Charlie this because she needed him to be there!

I can't pretend to know why this was changed between the two versions, but it was perhaps to account for the very situation that you described, in which Harriet was aware the murders were happening and wanted to wash her hands of it each time by changing her name and relocating.