oh I hope Willow is feeling better soon. I think it is normal after surgery to not poop for a couple days. I think if she is feeling pain, you will sense it. I think you should trust your instincts and if you are really worried, talk to your vet or take her in. It is just so tough with furbabies that they can't talk and tell us how they feel!!! Just like our human babies. HUg her, hold her and luv her!!! She deserves all the attention you can give her right now.
Kisses, Hugs and prayers for a quick recovery to Willow