The 22-year-old Clara visited a Winstead fan Instagram account, which posted a photo of the Fargo actress. After several of Winstead's fans lavished her with praise, Clara left behind a sick burn.
"Most beautiful and talented woman on earth? Oh man y'all are delusional. The girl is a piece of trash x," Clara wrote, reports PEOPLE.
Back in October 2017, paparazzi photos of McGregor, 47, and Winstead, 33, kissing surfaced, months after working together on the third season of FX's Fargo. At the time, McGregor was still married to his wife of 22 years, Eve Mavrakis, 52. It was also five months after Winstead split from husband Riley Stearns.
In January, McGregor filed for divorce, citing irreconcilable differences and seeking joint custody of their three minor children - Jamyan, 17; Esther, 16; and Anouk, 7. According to Us Weekly, Mavrakis asked for sole physical custody of the children and for McGregor to receive visitation rights.
McGregor infamously thanked both Winstead and Mavrakis when he won a Golden Globe for Fargo in January.
"I want to take a moment to just say thank you to Eve, who always stood by me for 22 years. And my four children, I love you," McGregor said. He later added, "There wouldn't have been a Ray without Mary Elizabeth Winstead," referring to his character from the show.
Mavrakis told The Daily Mail she did not like the speech, but refused to comment further.
Esther made a veiled comment about her father's new relationship in January, when she shared an Instagram clip where she sang an original song called "Made You a Man."
"Seeing those pictures, they're making me cry," she sang. "I don't know how to forgive... I don't know if I can."
While Clara might not have a great opinion of Winstead, she still enjoys sharing photos with her father on Instagram. On June 27, she shared a throwback photo of herself on the set of one of McGregor's films. On May 18, she also shared a photo with her estranged parents from her New York University graduation.
"That's a wrap. Thank you to my wonderful parents for giving me the gift of a full education," Clara wrote. "I feel truly grateful for this experience. AND that's the last time I'm ever wearing bright purple. Peace out Bobcats."
Clara herself made headlines in April for posing for Playboy. She intends on following her father into the acting business.
McGregor's next film is Disney's Christopher Robin, which opens on Aug. 3. He was also recently cast in Doctor Sleep, an adaptation of Stephen King's The Shining sequel.
Photo credit: Rob Kim/Getty Images for 2018 Tribeca Film Festival