My understanding is that if she is under three, and she orders off the children's menu at a sit-down restaurant, she has to pay, regardless. However, if she is under 3, she does have the option of eating off an adult's plate, with no issue.
At a buffet, she can have her own plate (ie, does not need to eat off an adult's plate), and you still don't have to pay for her.
We were there in May with our 2-year-old, and at sit-down restaurants, she shared a child's meal with her older sister, for no charge. At buffets, she had her own plate, and we were never charged.
HTH!
Linda