Student filmmaker Donahue shot to stardom as the lead character in the amateur psychological horror film in 1999 but she grew frustrated with showbusiness after struggling to find work following the movie's release.
She tells the Philadelphia Daily News, "I took all my stuff into the desert related to my acting career and burned it all."
Shortly thereafter, Donahue received a medical marijuana prescription to control her premenstrual syndrome (PMS) symptoms and she became such a strong believer in its effects, she began cultivating pot as a "solitary country girl" in California, in a bid to help others.
Now she's sharing her experiences with fans in GrowGirl, which is scheduled for release in America on 5 January (12).
And while fans of the Blair Witch movie may be disappointed to hear much of the film's memorabilia has been burned, Donahue reveals she did retain one keepsake - the iconic blue ski cap she wears throughout the film.
She adds, "That's the only thing I kept. I figured if things got really bad, I could always sell it on eBay."