It will not stunt her growth to have her spayed before the second heat cycle. Female sex hormones do not affect bone growth. If you have her spayed before her first heat cycle you will reduce her chance of developing breast cancer to almost zero. I would have her spayed now.
Talk to your veterinarian about your concerns and find out what their recommendations are. A lot of people have many opinions on this topic. I would take advice from someone knowledgeable who you trust--like your veterinarian. There are some breeders out there who will tell you not to spay your dog until later because they want to see how the dog turns out. Then when it is ~2years old and if your dog is a good specimen they will want you to breed or show.
Talk to your veterinarian about your concerns and find out what their recommendations are. A lot of people have many opinions on this topic. I would take advice from someone knowledgeable who you trust--like your veterinarian. There are some breeders out there who will tell you not to spay your dog until later because they want to see how the dog turns out. Then when it is ~2years old and if your dog is a good specimen they will want you to breed or show.