The MTV reality star and PEOPLE.com blogger, 34, was hospitalized in New York City on Thursday after doctors discovered a blockage in her kidneys.
Brown had been set to start chemotherapy on Tuesday after undergoing two emergency surgeries in mid-August following the news that she had been diagnosed with cancer for the third time.
"I was so frustrated that it seems my body keeps throwing me curve balls over and over," she tells PEOPLE. "It's hard to keep your spirit and your mind positive ... But I'm glad we are catching these curve balls and fixing them, one by one."
Brown had been working to regain some of the weight she lost after her surgeries in hopes of starting chemotherapy.
On Tuesday, "I was supposed to get my 'chemo cocktail,' but after they did the blood draw they saw a spike in my kidney levels, so they were only able to give me one of the two chemos," she says.
An ultrasound the next day revealed the source of the problem: a tumor blocking her kidneys. Facing excruciating back pain – "I didn't realize that all the back pain was because of my kidneys" – Brown was admitted to the ER on Thursday.
Courtesy Diem Brown
"I woke up from surgery and again amazed by my girlfriends!" she adds of her "IV specialist team," close pals Julie Rotundi and Alicia Quarles – who shared a photo via Instagram.
Brown has been sharing much of her struggle in hopes of giving others a look at the "realness" of her journey, she told PEOPLE in early September.
She is set to leave the hospital on Saturday – and in a recent Tweet, she showed off her glass-half-full attitude.
"frequent flyer miles for airlines & reward points for hotels…Any fun 'perk' upgrade card for hospital night stays? #GottaFindHumorInIt"
Friends have set up a support page for Brown on MedGift, a gift registry she founded to help those suffering from any illness.