Can you board the cats? If not - It's not a major issue. I have a dog, and it was actually helpful that during treatment I had to walk him. It got me out of the house! That said. I just remember a friend who had peritoneal cancer - she had one cat, and a husband luckily. They told her not to touch the litter box period, or handle the food. I think if she wants to keep them as long as someone does those two things for her, and she washes her hands after petting them, she should be okay. With chemo, cancer and facing possible radiation her immune system is severely compromised. This is why the precaution. I would ask the medical oncologist and surgeon what they think.

Take care and best of luck on the surgery! fingers crossed everything goes well.