Merrimac Girl Known As 'Mrs. Justin Bieber' Loses Battle With Brain Cancer

BOSTON (CBS) - A 6-year-old Merrimac girl battling brain cancer who captured the hearts of many and became known as Justin Bieber's wife has passed away.

Avalanna Routh made headlines back in February after meeting her "husband."

Bieber reacted to the news on Twitter.

"RIP Avalanna. i love you," he also wrote.

Bieber heard the story of how doctors and nurses at Dana-Farber set up a wedding for Avalanna at a Jimmy Fund event. There were flowers, a guitarist, and even a life-sized Bieber poster at the ceremony.

Bieber then flew Avalanna and her family to New York to arrange their Valentine's Day date.

After the date, Bieber tweeted about meeting Avalanna saying:

"that was one of the best things i have ever done. she was AWESOME! Feeling really inspired now! #MrsBieber"

Avalanna was battling AT/RT, an atypical teratoid rhabdoid tumor. It is a very rare form of brain cancer. Because less than 30 new cases of AT/RT are diagnosed in the U.S. each year, it is very difficult to acquire grant money for research.

Her family announced her passing on their Twitter page Wednesday morning:

"Our darling Avalanna went to Heaven this morning. Oh Avalanna, the brightest star - you took our hearts with you, our greatest Love;( "

Dana-Farber released this statement afterwards.

"We are saddened by the passing of Avalanna Routh. She was a very courageous young person who lived her life with grace and determination. By generously sharing her story, she raised awareness worldwide about atypical teratoid rhabdoid tumors and articulated the need for greater research of this rare cancer. Our thoughts are with her family."

Watch Avalanna's story from the 2012 Stand Up To Cancer telecast

There is currently no known cure for AT/RT.

If you'd like to donate to AT/RT research, visit cureatrt.org.