If she has little or no shooting experience, do not start her out on a center-fire handgun. Begin her training with a 22lr. A flinch developed from starting with to powerful of a weapon can be extremely difficult to overcome. Teach her proper technique on the 22lr and let her put several hundred rounds through it before moving her to center-fire. If you do that the transition will be easy for her. If she then starts to flinch with the center-fire it will be very short lived and she will have a good handle on the weapon within a few mags.
As others have said, let her shoot several different center-fire before making a decision on what to buy, but if one of the final candidates has a 22lr conversion available, like the Glock, encourage her to select that one and get a conversion at the same time or very shortly after you get the gun. She'll shoot a lot more if the ammo is cheap and the recoil is not punishing. There is no substitute for rounds down range. If she shoots 5 rounds of 22 for every round of SD ammo, she'll probably shoot about 5 times as much as she would otherwise.
A long gun is always better for SD, but with kids in the house she needs to be able to secure the weapon while still having fast access to it. A handgun in a nightstand safe beats the hell out of a long gun that is secured in a less convenient way. In a perfect world, she has both so she can grab the handgun fast to defend herself while retrieving the long gun.
As for selection of the long gun, it's hard to beat a light weight AR. Fast and deadly with 30 rounds available before having to worry about a reload. You can also minimize issues of over penetration by selecting varmint loads, like the 55 grain Hornady V-Max or 55 grain Federal Ballistic Tip for HD. I don't like shotguns because they are low capacity and are very slow to reload.
Just my thoughts.
As others have said, let her shoot several different center-fire before making a decision on what to buy, but if one of the final candidates has a 22lr conversion available, like the Glock, encourage her to select that one and get a conversion at the same time or very shortly after you get the gun. She'll shoot a lot more if the ammo is cheap and the recoil is not punishing. There is no substitute for rounds down range. If she shoots 5 rounds of 22 for every round of SD ammo, she'll probably shoot about 5 times as much as she would otherwise.
A long gun is always better for SD, but with kids in the house she needs to be able to secure the weapon while still having fast access to it. A handgun in a nightstand safe beats the hell out of a long gun that is secured in a less convenient way. In a perfect world, she has both so she can grab the handgun fast to defend herself while retrieving the long gun.
As for selection of the long gun, it's hard to beat a light weight AR. Fast and deadly with 30 rounds available before having to worry about a reload. You can also minimize issues of over penetration by selecting varmint loads, like the 55 grain Hornady V-Max or 55 grain Federal Ballistic Tip for HD. I don't like shotguns because they are low capacity and are very slow to reload.
Just my thoughts.