5' 5'' tall, which, while just about average height for a human, is positively GIANT by drow standards (who average 4' 9' for males and 4' 11'' for females). She'd stand a full head taller than most in a typical drow city like Menzoberranzan.
This is largely due to her diet growing up. Iliira was born on the surface and raised by a human man at a seaside inn. She ate a far greater variety of food, getting nutrients that even drow nobles tend to lack, as well as having much easier access to real meat and veggies instead of lichen paste, mushrooms, and insects, which forms the bulk of the typical drow diet (with nobles occasionally having rothé meat, and not even all that often).
It's also totally meant as a reference to the height difference between North and South Koreans, which is itself caused by the food differential. North Koreans do NOT get good or enough food as children, and as a result the average North Korean is something like six inches shorter than the average South Korean.