DUCK! Man alive do I love Princess Tutu so lemme just toss out lostcarnival as an option for her. It's about a traveling faerie carnival that stops in various different locations (Atlantis, party world, etc.) Characters can join the Carnival either accidentally to pay off debt or on purpose to get a wish fulfilled.

There are transformation aspects to the game: characters become more fae and can get things like sweet feathers or claws or such like that, which would be fun considering Duck's everything. There's plenty of opportunities to explore the setting, whether in the carnival itself or in the locations that they visit.

It's slow/medium paced and super backtag friendly. And lemme just slide a tdm link your way if you do decide to consider the game.