She is a nice size for her age, but she is still growing for sure. You would probably want to wait before you actually try her at breeding(like another half year or more). Especially now that she laid infertile so young, you would want her to fully recoup, and hopefully she will continue to grow. Another dragon that you have could have stimulated her to develop eggs. Maybe is she housed with another or maybe just every so often that she sees another was enough to stimulate her.