What is inexpensive and reliable? To me, a $600 AR chambered in 9mm with a 8" barrel seems functional.
https://palmettostatearmory.com/blem-psa-8-9mm-1-10-7-lightweight-m-lok-moe-sba3-pistol.html
Throw one of these one it and be done.
https://palmettostatearmory.com/holosun-micro-sight-dot-reticle-with-shake-awake-hs403b.html
Rural king sells 33 round knock off Glock mags for these @ $15 each.
9mm ammo pricing sucks still, but it is out there.
She needs to be the one to go shoot several variants of firearms in a manner to simulate engaging bad guys. Then, she can say what was effective and comfortable for her. Us suggesting a gun for her is like us thinking we know what tampon will be comfortable for her.
EDIT:
Rick and Jerrodh get it.