They could choose to leave them for sure, but… some of them end up being just really weak one-shots.
Shock Rounds and Cryo rounds are really the only two I can see playing even if I have another good option in my hand, but Hollow Points and Incendiary rounds are very much “I have nothing better to do”. And the idea behind loading a gun and not firing it is… odd. It assumes you are going to be firing a different gun, but why not put the ammo in that gun?
Also, I don’t think I’ve ever seen anyone actually load two ammo cards into Pride and Prejudice, unless it was on Wagner maybe. Because Pride and Prejudice is a great set of powers, and so you are likely to be using them again and again, which means they can’t stay loaded.
I’m not trying to say they are never useful, or that there isn’t advantages to them, but I see it as a clear place they could improve her deck engine, especially since the gun part is the more important part of her deck, and the part I’d least want to see changed (though, maybe making Pride and Prejudice a single card)