Firstly, welcome to TCS!
Did she have keyhole surgery or the regular kind? Is the swelling around the operation entry? Is she licking or pulling the stitches? Does the swelling appear to be bothering her?
I recommend that you call your vets and speak to them about the swelling. It might be that she is licking and pulling on the stitches and has caused some swelling. If this is the case, I would say that your vet will want to see her and will probably give her an injection of antibiotics to prevent infection.
Please check with your vet, they are the people who will be able to help!
Let us know how it goes! I hope she's better soon!