The 30-year-old fashion designer, along with her twin sister Ashley, was a far cry from the child star we came to know and love in the late '90s and early '00s.
Fast forward a decade, and the changes on the blonde beauty's face are definitely noticeable.
"The Olsen twins faces really look bad. Idk what bad botox or plastic surgery they did, but their faces look horrible," one fan wrote on Twitter, while another tweeted, "The Olsen twins look sick. That must suck to get plastic surgery then look in the mirror & see how it ruined you instead of [making] you better."
Mary-Kate in 2007 vs. 2017.
So has Mary-Kate gone under the knife? According to Miami plastic surgeon Dr. Rian Maercks, who has not treated the former actress, her transformation seems mainly due to smoking, not cosmetic surgery.
"I would say that technically the majority of the changes we see could be due to accelerated aging associated with nicotine products tobacco or other environmental factors, as she is a known smoker," he told Life & Style exclusively. "The most significant factors are eyebrow ptosis (the dropping of the brow), and atrophy of the periorbital (area around the eyes) and perioral area (the area around the mouth)."
He also explained how makeup and lighting may affect a person's appearance before adding, "It also appears that her bizygomatic width is increased (horizontal distance between high cheek bones). That only attracts attention to the temporal hollowing and lower facial aging changes."
However, Mary-Kate doesn't seem too concerned about the rumors.
"I think we're lucky [working hard] comes quite naturally for us," Mary-Kate recently told The Edit. "We don't need so much time to sit and think and ponder. But then I have a husband, two step-kids and a life; I have to go home and cook dinner. I ride horses on the weekends. You find the thing that helps you relax and if you don't have it, you have to look for it. Or you get burned out and then you're not productive."