Congratulations!!! I have 3 of them right now. I am really hoping to see little ones in with them one day but from all I have read it takes 2 to make babies. I am hoping at least one of them is a male. Maybe your little girl had been with a male before she came to live in your tank and finally felt comfortable enough to give you a baby. I don't know enough about them to know if they can hold on to fertilized eggs until conditions are just right. If you have had yours for a while and you only have the one I have to think they can.