Mean has the following meanings:-
1. Humble, possibly shabby: “She resided in a mean accommodation in Delhi..”
2. Repellent, selfish, petty; bad-tempered, vicious, unmanageable: “The mean nature of my boss pestered me to resign from the job.”
3. To have a purpose or an intention: “She didn’t really mean what she said.”
4. Middle position, half way between extremes: “The ship was stuck in the mean of the ocean when the tsunami occurred.”
Mien , on the other hand, means bearing, appearance, conducting oneself, or manner; especially, as it reveals an inner state of mind: “Some people are very efficient in hiding their inner self with their outer mien.”