Based off of your criteria, I would recommend a XD subcompact. My wife is about the same size (5'3", #105) and has petite hands as well. She absolutely loves the XD subcompact wit the pearce grip extension. It meets basically all of your criteria:
It has a small grip circumfrence with a relatively short trigger reach
Tall slide easy to get a firm grip on to rack the slide
Relatively light trigger, 5.5 lbs
13+1 rounds of 9mm
Usually polymer guns have smaller grips than steel framed guns due to not having grip panels
It does have a grip saftey, so without a proper grip on it, the gun wont fire.
Lastly, it has a loaded chamber indicator, so she will know when its loaded.
"The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government." - Thomas Jefferson