can you get her a little chicken or turkey and leave it on a plate for her, im sure she will be tempted, the cough may be because she had a pipe down her throat when she had the op and for what its worth i dont think the vets would have done an op straight away if you had taken her in as its quite a big operation , we all could have/would have done something different at one time or another with hindsight , i think you have to accept thats part of owning and loving your dogs , we can just do the best we can for them
concentrate on getting her up and walking again when the time is right