Stevie Nicks is grieving the loss of her Fleetwood Mac bandmate Christine McVie, who died on Wednesday, November 30, following a brief illness.

“A few hours ago, I was told that my best friend in the whole world since the first day of 1975 had passed away,” Stevie, 74, began in a handwritten note posted to Instagram.

“I didn’t even know she was ill … until late Saturday night. I wanted to be in London; I wanted to get to London — but we were told to wait,” she continued.

“So, since Saturday, one song has been swirling around in my head, over and over and over. I thought I might possibly get to sing it to her, and so, I’m singing it to her now. I always knew I would need these words one day,” the “Landslide” songstress continued, adding that it was the tune “Hallelujah” from the sister-group, Haim.

After writing out some of the more meaningful lyrics, the “Rhiannon” singer added, “See you on the other side, my love. Don’t forget me — Always, Stevie.”

The 2019 Rock and Roll Hall of Fame inductee joined Fleetwood Mac in 1975 with her then-partner, Lindsey Buckingham, helping take the band to a huge level of success. Along with Christine, their addition gave the group three talented lead vocalists and songwriters, each with their own different styles. Christine, who was also the band’s keyboardist, is best remembered for her classics, “Say You Love Me,” “You Make Loving Fun” and the iconic anthem “Don’t Stop.”

Fleetwood Mac’s 1977 album Rumors would become one of the best selling albums of all-time, moving 40 million copies worldwide, 20 million within the U.S. The LP reigned for an impressive 31 weeks at the top of the Billboard Top 200 album chart and went on to win the Grammy for Album of the Year. The group continued to produce albums and tour in the three decades that followed and was inducted into the Rock and Roll Hall of Fame in 1998.

Christine’s family broke the news of her sudden death. “She passed away peacefully at hospital this morning following a short illness. She was in the company of her family,” they revealed in a statement, adding, “We would like everyone to keep Christine in their hearts and remember the life of an incredible human being, and revered musician who was loved universally.”