It sounds like what my mother had not to long ago, which is bell's palsy, her whole right side she couldn't move or make a facial expression with. She didn't go to the doctor, but I did research and that is what she said she knew it was. After a few weeks it slowly went away on it's own. I believe a hospital visit is worthy for this. Here is a link explaining more about it. Hope it goes away soon.
Bell's palsy was my first thought when I read it.