Now 27, Wilson, who portrayed the late funnyman's daughter in the hit comedy when she was six, has recalled her last meeting with Williams in a blog post, revealing "I never could imagine losing Robin".
Wilson remembers running into her old friend when she was a student at New York University and he was filming August Rush in the Big Apple.
She writes, "He turned around, not sure what to make of the girl in the glasses and Nyu hoodie calling him like she knew him. 'It's me!' I said. 'It's Mara'... He told me how grown-up I looked and asked how I liked Nyu. It was small talk, but something about the way Robin looked at me made it feel like he truly cared. This was someone for whom everything mattered."
The former actress concludes her blog note by adding, "In the past few days I have said 'thanks' and 'I love you' to so many people. I'm fortunate to know people who care and have been so good to me, and it's heartening to know there are so many people who will miss Robin, too."
Her post links to another heartfelt tribute written by Lisa Jakub, who played Wilson's eldest sister in Mrs. Doubtfire.
Williams committed suicide at his home in Marin County, California last week (11Aug14). He was laid to rest in San Francisco, California on Sunday (17Aug14).