Lots of luck and good vibes for Iris today! I know how you feel, Pomegranate had her spay on Friday and I was a wreck leading up to it.
Make sure you have a variety of food on hand to tempt her to eat when she gets home, as she probably won’t really be interested in eating and if you’re like me you won’t be able to settle until you’ve seen her have something, even if the vet says she ate after the surgery. I got all of Pomegranate’s favourite greens in and she turned her head away from all of them! Have a banana or other nice fruit just in case she won’t take anything else.
Have water in a bowl that you leave close to her so she doesn’t have to move too much to drink, as she’s going to be pretty dopey for the first 12 hours or so.
Keep monitoring her temperature by feeling if her ears are cold. Make sure you have a hot water bottle or similar available, and loosely drape a blanket over her, so she can come out easily if she decides she’s warm enough.
I hope it all goes well today!