I think a SIG P229 (and related models) is a better lefty gun than rightie gun. The magazine release works better with the left index/trigger finger, the decocker also works well enough with the trigger finger, and the slide stop is just that, a slide stop, used for disassembly. In actual shooting, the slide is best released by an overhand grip-and-pull.
When shooting a P229 in rightie mode, the slide stop gets in the way when using a two-hand hold, and I must break my firing grip to get a thumb on the mag release. (My shooting thumb is NOT in the "high thumb" position, but if it were, as preferred by some shooters, the slide release would interfere.
FWIW, I am left-handed, but right-armed and right-legged. I shoot some handguns better rightie, and others lefty. I train with my serious defensive guns, such as my SIGs, using each hand as the weapon hand, both two-handed and one-handed.
I have related my experience with the P229, a double-stack autopistol that might be a bit wide for may women. The P239 is the single-stack cousin better suited for many smaller hands.
For a person who likes DA triggers, the DAK variant of the SIG models is even more ambi-friendly, as there is no decocker.
I also found Glocks to work slightly better as lefty guns than rightie guns, but I got away from Glocks due to hand fit issues, and though I don't have large hands for a guy, my hands are larger than those of most gals.
FWIW, most of my female co-workers select the S&W M&P40 as duty pistols, due to the adjustable/replaceable grip modules. The other choices, all .40s, are various Glocks, the XD, XDM, P229, and P226.