Lulu lost her parents to Sin at the age of five. She later lost her lover to Sin as well. She eventually took on the task of being Yuna's guardian, despite not even wanting Yuna to become a summoner, and knowing that both their lives could be lost to Sin as well. If that's not loyalty, I don't know what is.
Beyond her strength as a character and her skill with magic, Lulu marked a massive departure from the traditional black mage garb seen in the Final Fantasy series. Her style marries pearls, fur, lace, and lots and LOTS of belts, while she manipulates sentient dolls to do her bidding... like a classy voodoo dominatrix.
Other notable features of Lulu's design are her crimson red irises, beauty mark, and upscale hairdo. Her cleavage is all out there too, but luckily it's not of the backbreaking variety that Taki is known for.