Obviously you missed the part where I mentioned I love shooting our Smith & Weston .45 I'd carry that if I could but it's a little bulky.
Based on having helped two sisters, a daughter, my wife and a niece thorugh finding carry guns that work for them I offer the following observations:
Because you are used to a 1911, you might want to try the SIG P238 (an SAO .380 and very easy to conceal) and the SIG P938 (an SAO 9mm almost the same size as the P238 and also very easy to conceal. They are licensed copies of the Colt Mustang which is also a good candidate if you are willing to carry cocked and locked. My self, my sister's gentleman friend, and my wife each have a SIG P238 and like them a LOT. The P938 is a very new gun. There are some reviews of it and it seems to like to be kept squeaky clean or it might have extraction problems. The P238 is a totally mature product - all the new gun stuff was fixed a couple of years ago. Buy a new one and you won't have any problems. I know 5 people with P238's purchased in the last year and none of us have had a single issue with them.
In a slightly larger gun, you may find a 9mm S&W M&P Shield to work really well. I've fired both the S&W .45 and the Shield. The Shield has a trigger that, while it is a striker fired gun, is closer to the S&W .45, points well, is thin, relatively easy to conceal, and mine was failure free. The Shield is new but seems to be very reliable. Mine ate everything I fed it and came back for more. Nice gun. And priced around $460.00 it's more affordable than the SIGS.
The XDs .45, while it's a really little gun for a .45ACP, isn't as much of a handful as you might think. If you can find one to try, you might like it. It is definitely concealable, in fact it's more concealable than the Shield or Glock 26. It's the same size as the MK9 Kahr in the two dimensions that count, thickness and height. That said, it is a 'very' new gun on the market. I personally really like them, want one in the worst way, but won't buy one for a year. If I thought it was "The Gun" and I didn't have a gun, I'd get something else about the same size and follow its design maturity for an upgrade later. These are new and hard to get but they are also reasonably priced at about the same as Glocks and a hundred bux more than the Shield but less than new Kahr's.
I personally carry a Glock 26 a lot. It isn't that hard to hide, but it is a full quarter inch thicker than the Shield and XDS and that is a very important quarter inch when it comes to hiding a gun. My sister and niece love to shoot my Glock 26 but can't hide it, so they carry an LCP which they can 'always' hide. The LCP is like some kind of punishment to shoot but they suffer with it rather than being unarmed. My sister carries my brother-in-law's Glock 26 now and then but it's a pretty big lump on a petite 5'-1' frame.
If you don't like long light DAO triggers, all the Kahrs, Beretta Nano, Roarbaugh and Ruger LC9 are pretty much off the table unless you are willing to compromise. I had an LC9 and did not like to shoot it - it stung my hand. The CW9 Kahr does too, the Shield doesn't. Neither does the XDs.
My wife didn't like the LC9 or CW9 Kahr either - and couldn't manipulate the slide on either of them well enough to trust herself to carry it. I've fired lots of Kahrs, they make some good guns, especially the all steel ones, but I really do not like their trigger. That said, if you can stand the trigger and do the manual of arms with them, an MK9, a PM9 or even a CW9, in that order of desirability and more proven than the new CM9 are reasonable to conceal. You won't be thinking of any of them as pocket guns, so the few ounce weight penalty of the MK9 which makes it much nicer to shoot combined with it's small size could work for you if you can live with the trigger.
So, what did the sisters, daughter, and wife choose? Youngest sister and her daughter chose the LCP because they knew they would always carry it and were willing to put up with the trigger and sting when they shoot it. They wanted a P238 but the cost was not in their budget. Other sister picked a beautiful all steel .38 Special blued Colt Detective's Special from the mid 1980's with nice grips on it - it has a double action trigger to die for - must have been breathed on by someone years ago. If she hadn't bought it, I would have just because it is such a nice little gun. My wife, after going through 3 other guns (S&W 442, SP101, Ruger LCR) ended up with a SIG P238 and loves it.
Fitch