Sometimes, especially with significant others, it's possible that the only gun she will shoot and attain any level of familiarity with, is a 22 rifle. An AR, shotgun, Glock, etc. that she won't shoot regularly is useless. Maybe worse than useless. And if she doesn't enjoy shooting the gun in question, you can probably forget about attaining any level of familiarity.
If that is your situation (and it is my situation, too), then I see nothing wrong with a 22 semi-auto carbine. If she shoots the carbine well, it sure beats a can of pepper spray. If she shoots it really well, then she would be a very scary person to cross in a hallway. I know some women who are fiercely accurate with 22's.