Don't worry too much, she will likely outgrow it. When I was 12/13 I went vegetarian... of course I had no idea what I was doing, it only lasted about 9 months.
If she is eating dairy and eggs there are plenty of options. Mark has several posts on the subject and there's a number of members who are still.
I suggest not being pushy and just let her have her decision for now.
Also consider talking to her about humaneitarian eating (only consuming humanely raised food) maybe she will be more willing to eat meat?
(On being a humaneitarian | Humaneitarian)
Look for recipes for gluten-free vegetarians (another growing trend)