Valerie Bertinelli and Bonnie Franklin Credit: Jeff Kravitz/FilmMagic

Valerie Bertinelli is mourning the loss of her TV mom, Bonnie Franklin, who passed away on Friday at age 69 following a battle with pancreatic cancer. Franklin is most well-known for her role as Ann Romano on sitcom One Day at a Time -- a single mom to teenaged daughters Barbara (Bertinelli) and Julie (Mackenzie Phillips) in a high-rise apartment building tended to by a helpful superintendent, Schneider (Pat Harrington, Jr.)

"My heart is breaking," Bertinelli, 52, wrote in an emotional tribute on her website. She and Franklin reunited onscreen back in 2011 when Franklin guest-starred on Hot in Cleveland. "Bonnie has always been one of the most important women in my life and was a second mother to me," continued Bertinelli, who became a teen star on the CBS sitcom, which ran from 1975 to 1984.

Continued the actress: "The years on One Day At A Time were some of the happiest of my life, and along with Pat and Mackenzie we were a family in every way."

The late Emmy- and Golden Globe-nominated actress -- also a respected theater performer -- is survived by her mother, Claire Franklin, and stepchildren Jed and Julie Minoff.

"She taught me how to navigate this business and life itself with grace and humor, and to always be true to yourself," Bertinelli writes. "I will miss her terribly. "