What’s a gesture or behavior that instantly makes a woman seem classy?

It’s interesting that most of the traits in the answers so far are human traits and behaviors that aren’t gender-specific. To me, classy behavior comes down to how we treat each other and the integrity that we bring to the table. One very quick barometer is how a person treats the staff in a restaurant or any other situation where they’re the customer. Someone who’s terse or rude to a waiter or waitress immediately comes off as classless regardless of how expensive their attire might be.