Not sure what the OP's experience level is...
... so this may be way too basic, but just in case...
Remember that, in a given caliber, a smaller gun will be easier to carry, but will have more actual recoil and normally more perceived recoil. (A gun can potentially be designed to reduce its perceived recoil via grip shape and material, lower bore axis, and other design features.) Generally, the easier it is to carry and conceal, the tougher it will be to shoot, especially for a new shooter.
For home defense, you won't have to worry about carry and concealment, so it's normally better to bias toward the larger side (as far as the gun goes, not necessarily the caliber).
Remember that just like us men, women are all different. My lady is 5'8", athletic, grew up on a farm, and raises horses. She has plenty of hand strength, and her hands aren't all that much smaller than mine. She likes my Ruger GP100 .357 and my S&W 29-8 Mountain Gun .44 best (as far as handguns go), but she likes .38+P in the GP100 and .44Special in the MG better than full magnums (although she can shoot the magnums, and the .357 doesn't bother her too much, she's not a big fan of .44 magnum).
She doesn't mind the recoil of my S&W 13-3 with 3" barrel; however, she's still working on her DA trigger control, and as I have a bobbed hammer on that one, she has to shoot it DA, so it's not one of her favorites.
She has not liked the Ruger LCR I used to have, nor the S&W 442 I currently have. She also did not like the Kahr PM9. Small guns, with relatively sharp recoil, even in .38Special and 9mm. (And the LCR and 442 are DA only.) Note: the recoil of the PM9 doesn't cause pain, but the grip doesn't have room for her little finger, and the design of the PM9 (barrel slightly offset to reduce overall height) causes it to rotate slightly during muzzle rise. It's comfortable for me, but she doesn't like it, and neither does my best friend, primarily due to the torquey muzzle rise.
She liked my old CZ75 just fine, and doesn't mind my DW CBOB .45. They are both relatively heavy for their size, which helps keep recoil down. Both have full sized grips, and beavertails, which help a lot with controllability.
She keeps the S&W 29-8 in the nightstand, loaded with .44Special DPX, but her actual preferred HD gun is the Remington 870 in the bedroom closet, loaded with reduced recoil 00 followed by slugs (we live in the country, and 4-legged pests are a possibility; there are no kids so far, so we're not worried about penetrating interior walls).
My mother, on the other hand, is pushing 70 and has some mobility issues, and can't handle a shotgun comfortably. She's quite happy with a SIG P239, but normally practices with a SIG Mosquito .22 due to ammo costs.
I don't think you could pay my sister to handle a gun. She went to college in Boston in the 90's...
My ex, who was a tiny 5'2" 105lb thing, fell in love with a Beretta 92 Brigadier. She carried it in a purse, or her glove box. (The Brigadier is a beefed up variant of the M9; it is not small.)
As you have probably noticed, women, just like men, will sometimes surprise us with what they end up preferring. You've already said you'll have her look at corneredcat.com (a very good call, IMO); eventual next step should be to find some ranges that rent guns she's interested in, or find some friends who will let her try theirs, and see what she thinks after first handling the weapon(s), and then putting some rounds down range.
Last thing I'd recommend: Unless you and she are very good at working in an instructor-student dynamic, it's almost always the best bet to get an actual instructor to work with her. (Not to be sexist; women often have trouble teaching their husbands, too - it's the nature of many couples to resent any appearance of dominance.)
