"You can count me out all you want," she told PEOPLE on Oct. 2, a week before her latest setback. "But I'm not out. I'm fighting. I want to be here."
The MTV reality star, 34, was hospitalized in New York City on Friday in hopes of easing the chronic, debilitating pain that she has described as feeling "like a broken tailbone. It's unending."
Her symptoms have been so severe that she is down to just 100 lbs. – about 15 fewer than where she needs to be for her next round of chemotherapy later this month.
On Monday she was scheduled to undergo a procedure in which doctors insert a urine-drainage tube into her kidney in an effort to relieve persistent pain and swelling from various tumors and blockages.
Until now, The Challenge star says she has only found relief in a hot-button treatment: medical marijuana.
"I asked my doctor about it, and I'll be totally honest – I had never smoked before in my life," she told PEOPLE before her current hospitalization. "But I kept hearing everyone mention it. I'm taking all these synthetic drugs and they're not working, so I thought, 'I want to try it.' "
Armed with a medical marijuana card – in July, New York became the latest state to permit its use – "I did the vaporizer and it took away the pain and I finally felt like I was able to eat," she said. "That's what got me a pound higher."
"It's the only thing that helps," said the PEOPLE.com blogger, who is sometimes able to sip down her favorite treat: a "Simply PB" protein shake from Barry's Boot Camp in N.Y.C.
Other favorite munchies include Cheetos and pizza, which she is able to eat in brief windows.
Still, the road has been an especially tough one lately.
Courtesy Diem Brown
A Series of Setbacks"The setbacks terrify me – every single time it's been hard," she said of various complications she's endured, including an emergency surgery in mid-August and the recent hospitalization that partly delayed her treatment.
"You know, I finally get to do chemo," she said. "I get chemo, and then the very next day my kidneys start failing. And I have to have surgery, and recover from surgery, and they're telling that they're not going to be able to do that chemo over, so you have to get it together."
In addition to the complications, ongoing pain has posed the biggest challenge for the resilient star.
"At first my doctor thought I was depressed, because I was sleeping all the time and had no appetite," she said earlier this month. "And I go, 'I'm telling you, it's not that. If you take the pain away, I feel like myself again.' "
In recent weeks, Brown has been diving into fall football season (she's a hardcore Florida State fan), focusing on her plans to write a "no sugar-coating" cancer book and taking encouragement from the feedback she gets on social media.
"I read every single Instagram comment, and the reason why I favorite a lot of Tweets is because I want people to know I'm reading them," she said. "Sometimes I can't respond, because my mind is foggy or I just get really tired. But I want people to know I'm reading them and I'm so thankful."
Her positivity and fierce sense of humor – including a recent tongue-in-cheek Tweet about her pain medications, "Oh hello, #BreakingBad" – continue to inspire her friends and loved ones.
"Anyone else would probably go into a dark hole," says her close friend, Julie Rotondi. "She can be in the deepest haze and still one comment will perk her up. She's unbelievable."
One thing Brown can't abide: negativity.
"I believe in power and positive thinking, I can see myself with a family, I can see myself getting married, I see all of these things," she said. "I've had one or two brief moments where I felt like my body was shutting down no matter what my mind was thinking, and I'm like, 'What the hell? Shut up!' You legit have to start fighting with yourself. You can't let your mind go there, ever."
Friends have set up a support page for Brown on MedGift, a gift registry she founded to help those suffering from any illness.