According to the app update text, her name is Gaia ("the Legendary Nest Dragon") and, much like her brother, you send dragons on quests or races to complete the Legendary Nursery (her perch). Summoning her adds a bonus hatching slot and she can "hatch an egg once every four days".

Edit: The racetrack was updated, too. Only ten plays allowed a day (or 17 hours? I'm not sure...) and the prize-giving is different now. You get keys to open the chests and I've only gotten one or two for three chests. I'm not sure yet what signals to get one or two.