She's welcome to sit on an extra chair. She can observe that there's a pile of discarded of weapons in the corner, which tells that they likely should have had a battle, but skeletons be skeletons.

The skeletons have had years of practice in poker and aren't exactly easy opponents, but win or lose, they will honor their promise and open the door.

Behind the door is a boss monster: a giant minotaur with golden horns and golden hooves. However, this boss monster resembles the sin of Sloth, so it's just sleeping.

Next to it is a treasure chest.