The reality star, who rose to fame on MTV's Real World/Road Rules Challenge, died at 10:22 a.m. Friday in New York City. She had candidly chronicled her cancer fight in a blog for PEOPLE.com. Along the way, Brown became an advocate and inspiration for others facing similar battles, founding MedGift, a support registry for those suffering from any illness.
"I want people to know that the fight is worth it," she told PEOPLE in October. "And that's something that's so important for me."
Last month, Brown revealed the devastating news that the cancer that had been found in her stomach and colon in August had spread to her liver and lymph nodes.
"That was a shocker to me," she said at the time. "I was blown away. It really crushed a little bit of my spirit."
Friends and family had been gathering at her bedside at a New York City hospital this week as her condition worsened.
"Live as Hard and as Vigorously as You Can"Still, she remained fiercely determined to beat the disease and focus on the cancer-free life she dreamed of having one day.
"It's my personal perspective that you live as hard and as vigorously as you can," she said last month. "My goals are something I believe in, because I believe I'm going to make it."
Foremost among those goals was her dream of motherhood, something she wished for above all else.
"I'm going to have a family and get married and the whole American, 2½ kids, white-picket-fence dream," she said. "It's something that's really important to me, because it means a long-term future."
"Cancer Has Changed Who I Am"After first being diagnosed with ovarian cancer at 23, she faced the disease again in 2012.
"I know I will be fine," she Tweeted at the time. "I beat Cancer once & I'm gonna do it again! I know God has a reason for every speed bump in life & I'm ready."
The popular Challenge competitor beat the disease a second time and adopted a positive outlook for the future.
"Cancer has changed who I am," she told PEOPLE in August. "It sounds like a cliché, but I've only got this one life, and I need to live every day to the fullest. I'm a lot more appreciative of things now."
Just a few weeks later, her world was turned upside down once more when she collapsed with crippling stomach pains while filming a new reality competition. The devastating diagnosis: Her cancer had returned, this time in both her colon and stomach lining.
After two emergency surgeries, including a heartbreaking hysterectomy, she acknowledged going through dark days.
But even then, she held fast to hope.
"I'm trying not to think about the entire war," she said from her bed in the ICU at a New York City hospital, "but each battle at a time."
The battles kept coming, and in September, Brown said she had faced "terrifying" moments of fear about her future before pushing those thoughts from her mind.
"The setbacks terrify me – every single time it's been hard."
"Life Is So Beautiful"Being honest about her struggles and sharing them with others was of huge importance to the cancer activist, who bravely opened up about everything from her hair loss to her near-death experience in September.
"It's important to me to share the 'realness' of my journey," she said. "It's okay to admit that at times it's hard, that it can be tough."
She dreamed of experiencing everyday pleasures, like apple picking in the fall, but more than anything, she said, she just wanted to live.
"No matter what it is, you're going to have the bad days, but if you have hope throughout, you won, no matter what the results," she said in October. "Life is so beautiful."
Editor's note: While there have been numerous conflicting reports about Diem Brown's age, PEOPLE has been able to confirm, via public records and with family and friends, that she was born in 1980 and was 34 years old at the time of her death.