My sister has bell's palsy. what does this mean?

Facial paralysis: This is paralysis of one side of the face, usually of unknown or uncertain cause, although it can be a manifestation of lyme disease, occasionally herpes simplex infection.

Facial paralysis: Bell's palsy is a term for loss of function of the seventh facial nerve, the nerve that supplies the muscles of 1/2 of the face. It usually is of overnight onset, generally painless and felt to be due to inflammation of the nerve in its narrow exit canal from brain to face. It causes lid and mouth droop on one side. Most clear by six months; a few last and need surgical support.

Facial paralysis: She has weakness or paralysis of the muscles of facial expression. This may be due to a viral infection in the nerve. Fortunately most people with bell's palsy will eventually regain normal facial movement.