You have time to get her up to size if she's a good eater. I personally think age makes a bigger difference than size. A two year old at around 12-1300 grams will probably give you four eggs. If she has good body mass, they will probably be healthy and average size and hatch no problem. The only thing is, at only two years old, she may not even go...just depends on if she is ready or not.
If you wait another year, and she puts on some good weight, now you're looking at 6 - 8 eggs...