Still waiting for Dragons and don't have the books in front of me, but I think I may have stumbled upon something:
Per Wikipedia: "Everything that she has will be taken away by a younger and more beautiful queen, and then her valonqar (Valyrian for "little brother" or "younger brother") will strangle her to death. Cersei believes (whether correctly or not) that the younger, more beautiful queen is Margaery Tyrell and the valonqar is Tyrion Lannister."
Since I don't have the books, I can't verify the original wording, but perhaps "her" valonqar is referring to the younger queen's valonquar. Which means Margaery's younger brother Loras, Knight of Flowers, who was horribly injured by boiling oil, presumed dying, but status has not been verified...