Older female Calico with phobias

Our female Calico, "Yum Yum" is 14 years old. She has always been skinny, clean and healthy. In the past year she has gotten very finicky about drinking only fresh water especially in the bath tub. She has a scab near her hind quarters that she won't allow to heal because she keeps picking at it.
   
Yum Yum also seems to be constantly itchy on her head, near her ears.
   
I don't think these are normal behaviors and am concerned that she is not well. She does get regular vet check-ups. She also shares our home with her brother "Ko Ko"(both are fixed) We have had them both since they were kittens.
   
Any thoughts?

get an e collar(elizabethan collar from the vets office to allow her rear to heal. This will look uncomfortable but will help the area heal by not allowing her to reach it. Is she on flea prevention? Maybe she has ear mites? Does she have any hair loss on her head? Is she scratching her whole head or just ears or her mouth? Sometimes it isn't itchyness it can be a painful area or annoying spot for some other reason. take her to get a medicated bath at the vets office and have them show you how to put the collar on. Is she an inside only cat of inside/outside? What food is she on? Little more info please.

Yum Yum is scheduled for a visit to the vet next week.
   
We will ask some of the questions you have brought up.
   
Both cats eat Science Diet mixed with Dad's for older cats.
   
They are indoor cats.
   
Thanks