Ask yourself this, do you want her spayed when she is in good health and the vet is fully staffed and knows your dog or do you want to wait and run the risk of an emergency spay because of pyometra.
I would spay. Yes, there are risks, but it will be a one time thing. Her risk for pyometra &/or mastitis will be an every cycle thing. I would rather take one calculated risk than take multiple risks over the lifetime of the dog. Each cycle she has, you're gambling with her life. With something like that (a life) I'd prefer to take a calculated gamble one time than a lifetime of gambles. But that is just me. Blessings ...