The actress -- who was diagnosed with MS in August -- was honored at the 26th Annual Race to Erase MS Gala at The Beverly Hilton Hotel in Beverly Hills, California, on Friday night, where she gave a moving speech about living with the autoimmune disease.
"It would have been not only easy but understandable for Selma to hide when she received this diagnosis," Gellar said. "But instead she has done the exact opposite. She is facing this head-on and sharing this journey with the world."
"I don't think that there is a stronger person that I know and I am really proud to be your friend," the former Buffy the Vampire Slayer star tearfully expressed.
Taking the stage with her 7-year-old son Arthur, Blair began by candidly saying, "I have to say that I am afraid that I will fall, and I have the best fall-bearers in the world with Robin and Sarah and my son, Arthur."
"I am really happy. I am really happy that you are all here. That I get this chance to speak for so many people who don't get a chance to speak -- and oh my god, can you hear? I am talking really well," she proudly expressed.
Blair went on to thank Gellar for helping her land her first major role in Cruel Intentions. "I had 79 auditions before I got a job, and I got a great job. A really great job, and it was because of this woman," she said pointing to Gellar.
"She fought for me then and she is fighting for me now, and that's why this fight is so much easier," Blair shared, before directing herself to Roberts who "gave me a platform to speak for other people."
Blair also thanked the event's co-founder Nancy Davis, "who has made this an event that keeps people hoping and moving towards this goal."
"I have to tell you, everything is for our future, for the people who have immune diseases. My dream is that I get to be a useful mom as long as this kid wants me," she concluded.
Since revealing her diagnosis, Blair has been open about her MS and the difficulties that come with it, including doing her makeup and feeling fatigued. Just last week, she expressed on Instagram that she "cannot imagine ever feeling OK," but will get through it.
"Here’s a truth. I feel sick as all hell. I am vomiting and all the things which are not polite to speak of. My son ran away. From me. I have to get him to school," Blair wrote alongside a photo of her lying down in bed with a teddy bear. "The medical treatments take their toll. I am going to get through this. We do. This will pass."
"And to moms and dads who watch their kids sick on things we take to get better... I hold you," she continued. "So glad this is me and not my child. I cannot imagine ever feeling ok again. #roughday. We get through. #realitycheck."