The pair both got their big breaks in the hit 1995 teen movie, in which they played students at a posh Beverly Hills high school.
Silverstone paid tribute to the actress after the news of her untimely death broke on Sunday, claiming she'd always "feel love" for her one-time colleague.
She tells People.com, "I always felt connected to her as we shared a very special experience in our lives together. I feel love in my heart for her -- and hope she is at peace. This is truly sad.
"I'm so saddened to hear this news. I loved working with Brittany. She was so talented, so warm, and so sweet."
Meanwhile, Silverstone's fellow Clueless co-star, Scrubs' Donald Faison, remembers the tragic actress: "Brittany was one of the sweetest people you will ever meet. She had the voice of an angel and a genuine heart of gold. I'm very happy to have known and worked with such a special person. My heart goes out to all of her loved ones."
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