Can an adult have 'tics'/repetitive behavior issues? ?

There are a few cases of folks developing compulsive behaviors later in life. My own mother had a drinking problem and developed several "tics" when she wasn't drinking, the result of alcohol withdrawal. But, it is possible that your mother may have a psychological need for clearing her throat so often. Unfortunately, there isn't a lot you can do about it since the true reasons aren't 100% clear. As an aside, I drink water when my throat is dry! I think that's a bit more effective. Try suggesting it.