There is always a plethora of bad advice when people ask about guns for women. Revolvers and shotguns are terrible choices as they have a complicated manual of arms and are less robust and more prone to user error than modern semiautomatic pistols and rifles. Lightweight revolvers are especially difficult to shoot well. If a person lacks the strength to manipulate the slide on a pistol (usually due to poor technique rather than ability), then they lack the strength to repeatedly pull a heavy, long double action trigger and make accurate hits.
The advice to just let them shoot a bunch of guns and pick the one they like is similarly foolhardy. If a person is not educated in what makes a suitable defensive firearm, then they are incapable of making an educated decision.
I offer the same advice I offer anyone: buy a Glock or M&P in 9mm and seek professional training in its use.
With all due respect, Your "One size fits all Buy one auto and make them learn it from a pro mindset" is equally foolhardy... unless that expert also "prescribes" specific upper body exercises to build those muscles that are lacking in strength to allow them to rack the slide effectively.
And as another member pointed out, wheel guns are incredibly simple. If you pull the trigger and if it doesnt go boom, you pull again! (which is relatively instinctive) Its NOT instinctive to start tap/rack and other malfunction drills.
Yes, you can fire off MANY more rounds from an auto, but in many circumstances the first 2-3 are your most important.
Personally I'd rather have a simple 5-6 rounds "guaranteed" downrange in a couple seconds in a platform that is nearly 100% reliable over 15 rounds that may be prone to jams/malfunctions.
Squirt gun.
You never know how the relationship may end up.
If she is a new shooter or a female which doesn't shoot much. I'd recommend a revolver. If to be carried an aluminum frame/scadium .38 special, if to have at the house, like in night stand, then a four inch barreled revolver. It will be heavier, less recoil and better for learning shooting skills.
I wouldn't recommend the shotgun for a female not unless she has experience with shooting shotguns (skeet, trap, competitor, etc.) and she has a level of comfort. She obviously could learn, but wouldn't start with it.