Helena

The Queen Earth royal who sent Kanon to Earth in search of Nurse Angel, Helena also occasionally supports Ririka using telepathy. In the manga, she is the Nurse Angel of Queen Earth. Because Nurse Angels defend the planet only by their existence in the star system, she cannot support travel to Earth or Queen Earth will fall completely to Dark Joker. The state of Queen Earth is reflected in Helena, and due to Dark Joker's widespread corruption of the planet with the Black Vaccine she is extremely ill. Although she is holding off Dark Joker's invasion of Queen Earth by her own power, she continues to grow weaker from the effects of the Black Vaccine. Only finding the Flower of Life can save Princess Helena and Queen Earth.

Source: Based on Wikipedia character description.