Home defense with no intent to carry, I'd get my wife a 20 gauge.
x2, but I would still want her to have at least one gun she could carry if worst came to worst. Read the downplaying MS 13 Post- it's not like the guberment is going to protect us.
I also think a long gun handgun combo makes the most sense. start with what she shoots the best as I would venture the budget for 2 may not be there currently
if you have ever shot a handgun inside it is also not quiet , shorter the barrel louder they get
I hang a pair of electronic hearing protection off the magazine in the 223 rifle if there is 2 extra seconds to put them on then do if not they will fall to the floor , once on one hand can reach up and turn them on , you can now hear a floor board creak across the house yet will not be injured by the noise of shooting if you need to.
pistol caliber carbines have gotten good and more affordable the price of the Ruger PC carbine is about 450 can use Ruger or Glock mags , 9mm so one ammo , one mag type and run a long and short combo.
for transport the PC carbine is a take down it fits in a case that looks nothing like a gun case.
an expanding bullet choice placed in the target limits the over penetration issue through walls , anything that will be powerful enough for a stop will also go through some walls
if you choose 223 v-max go through fewer walls when they fragment as personal protection ammo it is called Hornady TAP-Urban I haven't tried walls but they seldom exit animals of any size.
v-max through walls
https://how-i-did-it.org/drywall/results.html