Sharon, stay calm, everything will turn out all right. I agree with others commenting on the need to let her stay overnight at the vet. My 14 yr old Jennie got spayed when she was ten years old. She had developed pyometra and she had also some breast tumors so she had double surgery, she got spayed and had three teats removed. She also got some teeth pulled out, not because she had a extra ones but because they were in a very poor condition, too loose when they were cleaned. In short, she did not stay overnight. She was scheduled for the morning 10.OO or 10.30 and I got her back around 19.00. So, I would also make sure it's absolutely necessary to leave her at the clinic. I don't think nobody is going to do a better monitoring of her than you. I wish you and her the best.
Rubi and
Jennie