Hi there! You need to allow her some time with her egg so that she doesn't lay a replacement egg. Generally they sit on the egg for 3-4 weeks then as long as you've removed any matey behavior and your not encouraging her to remain nesty and hormonal she should be ok.
I will post a helpful link for you. Also while one egg is ok..it wouldn't hurt just to tell your vet about this to put on file for future reference. When was she last seen by her vet? She is awfully young to be laying eggs already!6
Links.. Discouraging Breeding Behavior Sex and the.... Breeding behavior...
In the future if you need help it will be easier for you to find your post and it will get more attention if you make your own post