Still in use today - "Who's up for some/a [fun action]?" To which one can answer, "I'm game." I'm ready/willing. :)

This is an old-fashioned way of speaking. "game" as an adjective refers to someone who is ready for fun, adventurous, vivacious, and willing to get involved in new things. "they make them" refers to whoever creates human beings! So Evie is one of the gamest people ever created and put on this earth.

It is an older expression, and slightly cheeky. It means she is as [likely to engage in games / fun] as [any person you could hope to meet].