high gamma GT level

My 46 years old mom has elevated gamma GT levels for more than 5 years now. She is not an alcoholic and her other liver functions are more or less close to the normal levels. The gamma GT stays around 100 whereas the normal level is 60. Also, she complains of being fatigued after doing any sort of work, not necessarily anything stressful.

She suffers from erratic blood pressure but is otherwise healthy. Does anyone have an idea why she might have the problem of raised gamma GT?

Thanks in advance.