This info about Kaya is found at http://www.native-languages.org/wrongnames.htm
"KAYA: Baby name books claim this name means "little sister" or "elder sister" in Hopi. This is false. There is no word like this in Hopi, and I suspect this fraudulent name was intentionally made up because of the popularity of a Native American character named Kaya in the "American Girl" series of children's literature. In that book, the real name of the girl in the story was Kaya'aton'my', which means "one who arranges rocks" in Nez Perce
. Kaya'aton'my' truly is a real Nez Perce
word--the authors did their research...Since the target audience of young girls would never be able to remember and read a five syllable name all the time, I can sympathize with the authors' decision."
Kaya also exists as a girl's name in Japan, with many potential meanings. I picked out a few examples:
佳夜 "beautiful, good" + "night"
加悦 "to add, increase" + "joy"
夏椰 "summer" + "coconut tree"
花也 "flower" + "to be"