We're beyond bummed to report this news. Avalanna Routh, the adorable, six-year-old Justin Bieber fan known as "Mrs. Bieber," who touched our hearts when footage of her Valentine's Day date with The Biebs made national news, has died.

The little angel was from the Boston area and suffered from a rare and aggressive form of brain cancer. The condition is so rare, in fact, that only 30 cases per year are diagnosed in the U.S. and it is highly fatal.

Routh died Wednesday, Sept. 26, news which was tweeted by her heartbroken family.

Mrs. Bieber came to national attention since she was able to meet The Biebs and spend Valentine's Day with him thanks to a pretend wedding that hospital workers staged for her during treatment. A social media campaign went viral and caught The Biebs attention. He arranged to meet her in New York, and nothing, not even cancer, could wipe the smile off the beautiful little girl's face as she spent the day with her hubby!

The Associated Press reports that the Dana-Farber Cancer Institute praised Routh for raising awareness about the disease and need for more research.

The Biebs tweeted about Avalanna's death, and asked fans to pray for her.

R.I.P., Avalanna! Heaven is a more beautiful place now that you're there.

Watch Justin Bieber's Valentine's Date With Mrs. Bieber

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