personal assistant 
noun
A secretary or administrative assistant working exclusively for one particular person.A vice president might become an executive vice president, a secretary might become a personal assistant....
- While some rely too much on their personal assistants or secretaries, there are quite a few who believe that ‘self-help is the best help’.
- The secretary of the year competition was initiated to inspire and equip secretaries, office professionals and personal assistants to attain excellence.