He Xiangu was an actual figure from Taoist mythology. She is perhaps the only female of the Immortals (Lan Caihe is somewhat ambiguous), and lived during the Tang Dynasty (618 - 907 C.E.) a personage, perhaps Lao Tzu (the founder of Taoism) appeared to her in a dream when she was 14 or 15, and instructed her to eat powdered mica, which would make her immortal if she remained a virgin. In 707 C.E., she ascended into heaven to become an immortal. Her symbol is a lotus pod, which can improve one's physical and mental health.
In Jackie Chan Adventures, Tso Lan is seen defeated by a man, and Hsi Wu is seen defeated by a woman, so perhaps the two immortals were switched.