Buffalo Bills Linebacker and Fiancée Brittany Burns Were Planning Their Wedding Just Before Her 'Sudden' Death from Cancer

Brittany Burns was planning her wedding to her Buffalo Bills player fiancé right up until she died suddenly from ovarian cancer this week, a friend of the couple tells PEOPLE.

Tony Steward proposed to Burns, 26, in December – just days after she was diagnosed with a rare form of the disease.

"She was trying to plan [the wedding] while she was going through chemo, but she was always too sick," Tim Russell, Steward's best friend, tells PEOPLE of Burns.

"She thought that when she started getting better they'd be able to plan the wedding, but it didn't happen like that."

Burns and Steward began dating in March 2012 after meeting at Clemson University, where Burns was on the rowing team and Steward played football. As Steward's right-hand man, Russell recalled meeting Burns for the first time at one of the university's football games

"This girl with purple, dyed hair ran up behind me and hit me in my arm and said, 'you must be Tim.' That's the first time I met her," Russell says, noting that he was thrown off by her hair color. "She was super friendly, she didn't hold back at all. I'll never forget the day as long as I live. I knew she was going to be good for Tony"

The couple's love story is well-documented on social media, as the two often shared sweet photos of each other with heartwarming captions to match. Burns moved to Buffalo, New York, with Steward after he was drafted with the Buffalo Bills last year.

Burns received the life-altering news Dec. 9. Just three days later, surrounded by family at R2L restaurant in Philadelphia, Steward got down on one knee. But Russell says Steward had long planned to ask Burns to marry him.

"Me and Tony spent a lot of time shopping for the ring, way before he proposed," Russell tells PEOPLE. "I would say he was going to do it for, like, nine months. He got the ring before she got sick. He had the ring, like, two months prior to proposing."

Photos of the proposal show Steward down on one knee, placing the engagement ring on Burns' finger and the couple sporting big smiles in front of a Christmas tree.

One day later, Burns tweeted, "Still can't believe I get to marry @Tony_theTiger7."

Burns died in her family's Delaware home on Monday. Russell says her death came as a shock to him, Steward and Burns' family. The funeral is scheduled for Saturday at Westminster Presbyterian Church.

As the family copes with the tragic loss, Russell says he, along with Steward and Burns' family, are putting their energy into the woman's charity campaign, " Britt and Tony's Fight Like a Girl Campaign."

"All the money that was donated, it goes to research ovarian cancer," Russell says. "We're just getting our foot in the door in this fundraising thing, but it's going to grow. "It's not going to be a one-and-done thing."

As of Thursday, the fundraiser, on CrowdRise, has raised nearly $23,000.