It's normal to worry...you are a mom!
Just remember that the vet does this all the time and is great at it.
Suggestions:
Pre-Spay: Make sure you get the pre-op bloodwork done. It is very important for breeds that have predispositions to liver function problems, especially.
Also, go shopping now and get some Pedialyte, chicken broth, medicine dropper/syringe, nutrical, and Mineral Oil. Also, a soft doggie tshirt is all I needed for Mandie to keep her from licking her stitches, but you might want to look into a onsie (may need a premie size for her size). Shopping now is a good idea because not all stores carry premie clothes.
The reason for the things I mentioned are because these are what I needed for Mandie. I couldn't get her to eat the first couple of days and drizzling chicken broth on her kibble made her gobble it up! Oh! I would also see if you can get Chloe to eat some green beans and/or carrots. I say that because of why I listed the mineral oil. Mandie had a hard time pooping after surgery (probably due to the meds). Mineral oil mixed with her food and even some rubbed on her bum helped. But, if I'd a thought about it..I would have upped her fiber intake before hand to help.
The Pedialyte and dropper or syringe is because on the first day, she wouldn't drink water either. So, I did that by hand. By the second day, she was drinking on her own.