Grammar Naziism

Just a little post for a little thought. This exchange is adapted from the script for my smash-hit play, Eternity in the Hearts of Men:

GRAY
It was a donation.

DOROTHY
From who?

Did that make you cringe a little? Yeah, me too. It should be "From whom?", huh? Every time I read that line or hear it spoken aloud I feel a little twinge of shame. So why not fix it? (I'm sure you're one step ahead of me already.)

Because I'm not writing a science paper or a newspaper article or a medical brochure. I'm not writing prose or a poem. I'm writing a character. Some characters speak perfect English and some do not.

It sounds wrong, but I know that if Dorothy said "whom" it would sound even wronger.