As a rule, I encourage parents to feed their kids the same diet they feed themselves. A vegetarian diet is perfectly healthy at any age as long as it provides the same amounts of protein found in meat- or fish-based diets. This is relatively easy to achieve, since proteins can be found in lentils, peas, and beans; dairy products; eggs; nut and seed purées such as peanut butter or tahini; and soy products such as tofu or veggie burgers.
Some kids, especially young girls, spontaneously adopt a vegetarian diet on their own, often as part of a trend they pick up at school. Don’t tell your little Buddhist, but this usually lasts no more than a year. As long as you ensure that she gets adequate and diverse nutrition from such foods as those listed above, you need not try to force or convince her to eat meat. She will grow up just fine, even if this phase lasts longer than a year.