Cat damage to trees

Earlier this year I discovered that my 20yr old cat had taken to scratching the bark of my Viburnum opulis[?], given to me by a friend who discarded it in favour of carlesii [sp?] as he had a very tiny garden. I looked out of my window one morning to see the bush vibrating as if it were having fits! By the time I spotted this the damage was right round the trunk, but fortunately it has branched lower down after being rescued. Should I cut off the yellowed top?
Later I found that she had been at the standard olive. It has damage about half way round and halfway up the 3ft stem. It's leaves have yellowed a little and only a few of the baby olives continued growing. Any ideas about how I can help it recover, apart from shooting the moggy?
The odd thing is she has never done this before, usually preferring a fence post.

 

I do not have a mog[ passed away ]anymore. It may be pos to rig up a scratching post therby saving your shrubs. Your plants may recover.

 

great sign