You indicated that she recently was spayed. This could be for a couple of reasons. It could be from hairballs. You can add a couple of spoons of canned pumpkin (not pumpkin pie filling to her food every day. This will help prevent hairballs and also keep her regulated with her potty habits and prevent constipation. Second, when they spay a cat, a tub for breathing is inserted into their throat. This is an irritant, and they may have bruised her throat or vocal cords with the intubation. If she is still doing this in another few days and hasn't produced a hairball, I believe she needs to see the vet. Let them know that you were advised it could be a result of her intubation during her surgery.
Please let me know if I can assist further.