'Mrs. Bieber' joins Justin on the Today Show

NEW YORK (WHDH) -- Thousands of Justin Bieber fans were in New York to watch him perform on the Today Show Friday, but only one fan was his special guest.

Merrimac’s Avalanna Routh -- known to many as ‘Mrs. Bieber’ -- spent some time with the superstar.

Avalanna, 6, has a very rare form of cancer known as AT/RT.

Her love of all things is Justin Bieber, who helps her get her though her long days of radiation treatment. So much so, the Jimmy Fund arranged a pretend wedding for her.

“There was a paper cutout of me and she did the whole wedding with the paper cutout,” said Bieber.

Avalanna’s dream came true in February when she met the pop superstar -- thanks to a Facebook page set up by family and friends.

The two have kept in touch ever since.

“We talk on iChat all the time and I see her on Facetime,” said Bieber.

Check out the video to see Avalanna and Justin on the Today Show.