Since you haven't purchased yet, I'll chime in on the two calibers you haven't shot yet.
I have both of Sig's small pistols, the P232 in .380 and the P239 in .40S&W. Love em both, but the 232 is the one that gets carried most. Reason? Weight (and I don't have a decent holster for the 239 yet). They're both effectively the same size, but the 232 is light enough to just tuck and go.
The 239 is available in .40S&W, .357SIG and 9mm Luger. If you get either the .40S&W or the .357SIG, you can get an aftermarket barrel for around $200 (from Barstow and others, not from Sig) that allows you to convert it to 9x19. (The 9mm model can't go the other way though.)
Other makers' models in these calibers I can't comment on, but mine have been flawless from the start. I got the 232 used, and the 239 new. You should be able to find either used within your price range.
The 232's light weight (mine is around 25 oz fully loaded) makes it a bit snappy on the recoil, and given your size, you might suffer from slide bite, but it might be a good choice for your wife. For my particular hands, none of my other guns points so perfectly.
The 239 has plenty of power, weighs about 33 oz loaded (8 rounds of 180gr .40S&W), is small enough to conceal, and used, might be in your price range.
Both have a decocker, so can be carried with the hammer down. Should I ever really, really need it, I don't have to worry about "did I remember to take the safety off", I'll simply draw, and if necessary, pull the trigger. Just like a revolver.
My 3 cents worth.
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Oh, and regarding that Ruger P90 question. Nice gun, aluminum frame reduces the weight, but there are many less bulky options if you want to carry a .45ACP. And the safety (at least on mine) doubles as the decocker, so once decocked I have to remember to flip the safety back off to make it ready to fire upon drawing. In IDPA, sometimes I've forgotten. In real life, I wouldn't want to have to worry about it, so it will never be my carry gun. That, and at 5'8", I can't conceal it - too big. At 6'2", you might be able to swing it.
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One other thing I just thought of. All three of the above guns (at least mine) are available in rust-resistant materials. The 232 in either stainless steel or anodized aluminum (frame) with a blued slide. The 239 is blackened stainless steel, and the P90 is aluminum framed.