I'm sure you've put a great deal of research and thought into this decision, and that's all any of us can do in these situations. I also believe you've made the right decision for your baby girl, and with your love and excellent care she will be back to normal before you know it. I've always had my babies spayed and neutered, and I believe it has made their lives better by them no longer being ruled by their hormones going crazy.
Spay day may be easier for you if you and your wife plan activities that will keep you busy for most of the day. My vet wanted to keep Puff overnight, but when I discovered that she would be alone all night we came to agreement that she would be better off at home under vigilant observation. I also strongly recommend having pain meds on hand.
I'm sure all 3 of you will come through this ordeal just fine.
BTW are you still considering adding a baby brother or sister to your family?
__________________  Shannon & Puff 
"All his life he tried to be a good person. Many times, however, he failed; for after all he was only human. He wasn't a dog." Charles M. Schultz |