Justin Bieber Valentine’s date: a 6-year-old girl with cancer

He called her "Mrs. Bieber" — making her the envy of girls worldwide.

Avalanna Routh, a 6-year-old Beiber fan — she claims she's been a fan for an impossible 80 years — battling a rare form of cancer known as atypical teratoid rhabdoid tumour (or AT/RT), had the Valentine's date of her life this year.

Last year, hospital staff arranged for young Routh to "marry" her crush in a ceremony complete with flower, cake, music and a cardboard cut-out of Bieber. Soon after, a Facebook campaign was launched "to help the little girl meet her 'Mr.'"

Justin Bieber, upon hearing her story, flew her and her family from Massachusetts to Manhattan to spend the day with him.

"I got Bieber fever," the little girl told NBC News.

The low-key "couple" played Candyland, snacked on Sour Patch Kids and cupcakes, signed autographs for each other, and then Routh played with the pop star's iconic hair.

"It was great…He wants to be my husband," Routh told CNN.

Perhaps Selena Gomez should look out? (I kid, Bieber fans. I kid.)

"That was one of the best things I have ever done," Bieber tweeted that day. "She was AWESOME. Feeling really inspired right now."

"This is a beautiful story," Aileen, Routh's mother, told CNN, "and we need to keep the momentum going and we need to fund finding a cure for AT/RT."

The illness is usually fatal within 9 months, but Routh has been beating the odds, fighting the "very aggressive, rare disease" for five and a half years "with grace and humour."