Some questions about showdown

[Guest alexos879]

Hi,

I play my wife in poker sometimes at home and we have run into some questions about showdowns.

What are the rules regarding showing cards? Let's say it is the river and I am first to act. I check and then she checks. I show my

two cards and then she shows one of her cards which is enough to win the pot. Is she required to show both or is she able to just

show one?

Same situation as above except I show one card which is enough to win the pot, and she mucks. Can she demand that I show the other

card, even if she has mucked?

Thanks