Im not one for good "advice"
But i can re-assure you that millions of puppies are spayed each year and come out of it fine. Our baby is only 5lbs now and was probobly neutered at about 2.5 lbs maybe? Im never good with the figures though. But needless to say he came out fine with no problems. Just give her lots of love, and im pretty sure she loves you more so that will help her through the surgery. Just keep it as stress free for her as possible. Im sure one of the more experienced people will post some better advice but i hope this helps you out, and keep us posted on how she does.