Perhaps one of Demi's two closest friends is actor Matthew Scott Montgomery. In a 2019 Instagram post dedicated to Matthew and her other closest friend, Sara Elizabeth Mitchell (who goes by Sirah), Demi wrote, "Thank you for never leaving me in my darkest moments, for always drying my tears. . . . I'm so lucky to be best friends with two incredible souls who are so talented and creative because it inspires me daily. . . . most importantly you never abandoned me like others did when I was going through sh*t.. you were there to listen, without judgement and only love and I can never fully express what that means to me. You're the greatest friends I've EVER had and our future together is so bright. I love you both more than you can imagine!! Thank you for this past week."
After Demi's 2018 relapse, Matthew, who was at the time in a show called Dead Boys, spoke out about his best friend's struggles on his Instagram Story. "It's been an incredibly difficult few days, and this year has easily been the hardest I've ever experienced. I will miss hearing my best friend's laugh, maybe my favourite sound in the world, in the audience for these final shows as she continues to recover." Matthew went on to say in the Harper's Bazaar interview in May that Demi is a "fighter in every sense of the word."