Just as long as they watch her like a hawk, they're fine. Vets aren't usually excited to do a heat spay but they usually will... and honeslty, it's good that she went through one heat before being spayed. It gets the hormones flowing and allows the growth plates to close sooner, causing shorter bones that are less likely to be weak and break. I'll always make sure to let my dogs go through at least one heat before spaying.