I don´t wish to be picky but Princess and Sheikha aren't the same,much like Duke or Princess,They are really all royal titles but they shouldn´t be baffled: but being an Emirati I believed I could response your question about sending cards to Royals in this article while in the U.A.E. https://edgarvhtfp.dm-blog.com/32967895/the-single-best-strategy-to-use-for-dubai-royal-family-members