Thank you for your question. The first recommendation is to consult with your veterinarian and rule out any possible medical conditions that could cause this behavior. Some medical problems where licking is an indicator are: Cushing's Disease, liver disease, neurological, stress - these are just to name a few possibilities. Your dog could be doing this for any number of reasons - the first is habit. She may have been doing this behavior before you had her. Habits can be hard to break and can turn into obsessive behaviors. Considerations to help change what she is doing: boredom - increase meaningful exercise - both mentally and physically. You can try interactive dog puzzle toys that cause her to focus and solve problems, food stuffed treat toys like the Kong or the Bob-A-Lot. Outdoor walks for exercise and exploration. If she is social with other dogs, playtimes. Anything that would be appropriate for her to disperse energy and give her something different to tire her out. Covering the couch is a good idea - you can cover with a blanket, however she may end up licking the blanket. Veterinary consultation first. If there are no medical conditions indicated, try some of the options listed. After this you can contact a trainer or veterinary behaviorist who uses positive training methods for a behavior modification program. I've attached a link with great information and training ideas. I hope this helps.