It sounds like you have a great vet. I'm waiting until Archer turns two to neuter because research says that early spay/neuter can affect their bone development and overall health. There should be plenty of threads on the forum with links to studies and tons of information. So if you can wait I'd highly suggest you do. Just waiting until shes had one heat cycle would be good enough for me. If you feel like you couldn't properly protect Maci from an accidental pregnancy during that time then I would spay before her first heat but not before 6 months. You'd have to be very careful to make sure she was never alone outside for the entirety of her heat, which is kind of a long time.