I am not. I agree with you that it is obvious. I was trying to prove to my opponent that she needed to show me her treasures when she bought a card.
If I was playing with someone who tried to pull something like that, they would quickly find themselves on my "people I don't play games with" list.
But you do not have to play (or reveal) all of your Treasures, just enough to generate the amount you want to spend. It is often sensible to hide the fact that you drew into all of your Gold early in a shuffle.
Yeah, that is an important distinction.
As Donald said, she has to show you all the cards she
plays, not all of her cards.
In my clean-up phase I make it a habit to scoop my played cards on top of my unplayed cards before putting them in my discard pile.
That way I don't reveal any of my unplayed cards.
You never want to give your opponent more info than you need to.