Myrcella doesn't die in the books

Jaime Lannister never goes to Dorne in the books as mentioned earlier. Although  factions in Dorne are similarly angered at the Lannisters for Oberyn's death and are ready for revenge. In one of the many plots brewing  Myrcella is badly wounded in one of the escapes — when someone tries to kill her, one of her ears is chopped off. Gruesome but definitely no death. But she's still alive in the books and at the close of A Dance With Dragons she is on her way back to King's Landing.