Try on Andy's ring.

"Here, let me try your ring on. You think the same thing will happen to me?" you say. Andy looks at you blankly and passes you his ring, his hand shaking slightly. You take the ring. It feels lighter than you had expected. It feels like it's not even real metal!

You take a deep breath to dispel your gathering nerves, and slip on the ring, braced for some kind of pain. Nothing. After several long seconds you open your eyes to find yourself still looking down at Andy from the exact same height. Either I'm a really tall girl, or it didn't work. You look down at your body and see the familiar outline of a man-sized chest; your clothes still fit you perfectly. Obviously not a girl, then.

Andy seems to be recovering slightly, and now looks curious enough to make a suggestion. "Maybe mine only works for me? Go try yours on."