When Isabella Rossellini first met Laura Dern on the set of 1986 cult classic “Blue Velvet,” she thought Dern was blind.

A source told us that at a recent screening of Dern’s new film “Marriage Story,” “Isabella told a very funny story about meeting Laura … She assumed Laura was blind because she so brilliantly played a blind character in ‘Mask,’ and literally held Laura’s arm to guide her around to introduce her to people on set.”

When Rossellini finally observed, “You’re not blind?” Dern told her, “No, I’m an actress.”

Despite any misunderstanding, Dern tells Krista Smith on Netflix podcast “Present Company” that Rossellini “was such a mentor … We were working together and we were girlfriends, but she was just older enough that she was already dealing with marriage, divorce, babies, love stories, being less attached to everything.”

Dern then recalled becoming close with her younger “Fault in Our Stars” co-star Shailene Woodley. “We became like sisters — and I was playing her mother — but I mean, she moved into my house for a while. We really were like best girlfriends, and I think [that’s what] women who are slightly older than me did for me.”