[Fritz n Sophie]

Hi everyone. I've been on here a little bit but I am fairly new. My little girl Sophie is 5 months now and I am concerned about what to do when she goes through her first heat. The vet I use (and love) doesn't want to spay her until she is full grown because she is so small. Better safe than sorry. Anyway, all of my female dogs in the past (long past) all were spayed when they were about 6 months if I remember correctly and they didn't go through heat. What do I need to do? Any idea when this will probably take place? I just want to be prepared for her once it happens.