Sian Barbara Allen, a Golden Globe-nominated TV actress who appeared in such hits as The Waltons and L.A. Law, died today at the age of 78 in Chapel Hill, N.C. The cause of death was Alzheimer’s Disease.

A prolific television performer of the ’70s and ’80s, Allen was born on July 12, 1946 in Reading, Penn. Raised by her mother and grandmother, upon graduating high school, she received a scholarship to the Pasadena Playhouse, which sparked her career. She studied with the highly regarded acting teacher Peggy Feury as part of the Journeyman program at the storied Mark Taper Forum.

Afterward, she was soon hired as one of the last contract players at Universal Studios, eventually booking roles on such series like Gunsmoke, Cagney & Lacey, The Incredible Hulk, Hawaii Five-0, Columbo, The Rockford Files and others. She was also the first woman to pen a script for an episode of Baretta, in 1978.

On the film side, she starred in You’ll Like My Mother, featuring Patty Duke, Rosemary Murphy and Richard Thomas, which garnered her the Golden Globe nod for most promising new actress in 1973. She followed that up with an appearance in the Bette Davis thriller Scream, Pretty Peggy. Other roles include the Western Billy Two Hats opposite Gregory Peck and Jack Warden and The Lindbergh Kidnapping Case with Anthony Hopkins.

“Sian was most often cast in roles in which her characters showed great vulnerability and uncommon empathy, which won her a legion of fans all over the world,” her obituary reads. “Sian also performed in the theatre. One of her favorite roles was Emily Webb in OUR TOWN at the Williamstown Theatre Festival in 1976. Sian later named her daughter Emily in honor of this beloved character.”

One of Allen’s proudest achievements was receiving the Key to the City of her hometown. After leaving the industry in 1990, Sian maintained an intense focus on politics. Along with then-husband, Peter Gelblum, and daughter, Emily, she volunteered for Jackie Goldberg’s 1993 city council campaign in Los Angeles, was a “staunch supporter of Cesar Chavez and the United Farm Workers and never crossed a picket line in her entire life,” her family said. She was also a “remarkable poet and leaves behind boxes of writing.”

Allen is survived by her daughter, two sisters, nephew, ex-husband, cousins and grandson, Arlo Fonseca, “who made her laugh more than anyone could dream.”