Lilith Sternin is Frasier Crane's wife. She is portrayed by Bebe Neuwirth.
Also a psychiatrist, she is very logical, and virtually never shows any outward signs of emotion. Late in the series, Sternin had an affair with Dr. Louis Pascal, which resulted in the couples separation and Pascal's insanity. Lilith and Frasier eventually divorce sometime between the Cheers finale and the pilot of Frasier (TV series), despite having reconciled in "The Bar Manager, the Shrink, His Wife, and Her Lover".
Lilith has a mother named Betty Sternin who once appeared to force Lilith and Frasier into renewing their vows in a second wedding due to having not been invited to the first, and a half-brother named Blaine who is a con-artist not unlike Harry "The Hat" Gittes. Lilith and Frasier's son Frederick Crane continues to live with her in Boston while his father moved on to Seattle.
Lilith has apparently had strained relationships with members of the Crane Family as on Frasier's spin-off series, her former mother in-law Hester Crane once referred to her as the "icicle" as well as her (then) father in-law Martin Crane refers to Lilith as being weird saying; "No, Maris is a little strange. Lilith is just weird." Lilith also had a one-sided rivalry with Frasier's brother Niles and his wife Maris for snickering during the recitation of her wedding vows. Many members of the Crane family would go on to foretell Lilith's arrival by a chilling drop in the temperature, and flocks of birds fleeing en-masse, as well as Daphne Moon having a sudden headache each time Lilith visits.
Lilith along with Frasier also appeared in a single episode of Wings, "Planes, Trains and Visiting Cranes". Sternin appears in the spin-off series Frasier twelve times. Neuwirth was asked to become a regular character, but declined due to fears of pigeonholing. Grammer himself said he didn't want to ask her back as he felt the only way the spin-off would work is if Frasier was on his own. She wanted to return to Broadway. You can find more about her appearances on Frasier here