Immortality =/= OP though. Maybe mention her control of the laws of nature or whatever within the Crimson Sky instead. XD

That being said, 100+ year old being romantically interested in any normal aged human being is pretty normal, and even justified if you consider how Rui-Ling is 'Frozen' in the body of a horny teenager going through puberty. And hey, elves and vampires and divine beings make babies with mortals all the time, and no one thinks that as creepy~