Even though she is 14 months I wouldn't breed her as it's her first heat. She will probably have hard enough time figuring out what it happening to her the now never mind ending up pregnant.
I sound like I am talking about a human here haha, but I do believe its too early for her. She was later to mature so I don't think she would be ready for motherhood yet.
I'm not going to hark on but think about all the costs involved and the heartbreak you might end up with. Premature pups, emergency c-sections, your beloved little girl dying in childbirth.
On the other hand there are a lot of positives, it's up to you to weigh them up. At the end of the day its your descision and we can only provide you with information and opinions to help you make that descision.
I found this site and all of the links VERY helpful. Hope it helps you decide. Good luck in whatever you do.
So you want to breed, I want to breed my Dog, Should I breed My Dog?