Similar markings, but I've never seen a milk snake with a head like that.

Sure as hell looks like a dang Pit Viper (of the "Cotton Mouth" Water Moccasin variety) to me! I can't tell squat about size from that pic with no reference to compare with. You didn't mention what happened to the lady after being bitten. Did she ignore it? Go to the doc? Receive anti-venom? Die?

All I know is, I try to avoid ANY snake with a diamond shaped head. 'Course, anytime I've been as close to a moccasin as that photographer, it's mouth was open and there was no mistaking what I was looking at! Just the fact that snake isn't acting more aggressively being cornered like that, I'd doubt it being a moccasin.

That said, I don't know where this lady lives, so that would be a clue. If she's in Idaho (for example), I'd say water snake. I know many people confuse a Northern water snake for a moccasin, but I really can't tell from that pic and would avoid it anydamnway just from looking at that head!