Amethyst, Princess of Gemworld Vol. 1 (1983)

Plot

Reaching 13 years old is a milestone in life, especially in the case of Amy Winston. It's on that birthday that Amy discovers many hidden truths about her past, foremost that she is actually Princess Amethyst and comes from a world much different from her own, the Gemworld which is far removed in time and space from planet Earth. Her eventual return to her family will not be without surprises and challenges.