The Kiss of Deception by Mary E. Pearson
In a society steeped in tradition, Princess Lia’s life follows a
preordained course. As First Daughter, she is expected to have the
revered gift of sight—but she doesn’t—and she knows her parents are
perpetrating a sham when they arrange her marriage to secure an
alliance with a neighboring kingdom—to a prince she has never met.
On the morning of her wedding, Lia flees to a distant village. She
settles into a new life, hopeful when two mysterious and handsome
strangers arrive—and unaware that one is the jilted prince and the
other an assassin sent to kill her. Deception abounds, and Lia finds
herself on the brink of unlocking perilous secrets—even as she finds
herself falling in love.
This review mentions Lia's going through the painstaking process of having a wedding kavah tattooed on her back (like a henna tattoo but a little more painful). And one previous searcher remembers the tattoo as supposed to be temporary but in Lia's case, as she doesn’t marry, it becoming more and more vivid.