Valerie Bertinelli on Mackenzie's Arrest

Mackenzie Phillips's former co-star on One Day at a Time, Valerie Bertinelli, is opening up about the actress's drug bust.

Valerie tells ET, "Mackenzie is a very good, good, sweethearted woman who obviously is going through an amazingly difficult time. She doesn't need our judgement, she just needs our prayers."

Bertinelli continues, "We both have an incredible amount of faith in Mack. Mack is strong, a wonderfully strong woman."

Even though the two haven't worked together in years, Valerie says she has nothing but the warmest regards for her TV big sis. " I love her to death," she says. "She knows how much I love her and I'm always there for her, always."

Mackenzie Phillips was arrested yesterday during security screening at LAX for allegedly possessing cocaine and heroin. The daughter of the late John Phillips has had a long history of drug abuse, but got clean in 1992.

When she was taken into custody, officer reportedly noticed track marks on both her arms and asked if she was a diabetic.  According to the police report, Phillips responded, "No, I am healthy except for my drug problem."