I would take her back to the Vet for a POC, we rarely see bitches back post-spay, but once in a while we see one which seems to be in pain. Most bitches within 24-48hrs of the spay are trying to do too much. Sometimes the sutures used in the muscle layer cause irritation, or perhaps the wound is slighlty tight. Is there any redness or swelling? Our Vizsla bitch, despite the wound being normal and all ok was a complete wimp and whined and groaned her way through the 10 days until the stitches came out. Better to check with the vet though. Hope she is ok soon.