Her family described Bronwen as “the greatest sister, daughter and friend” and said they had been left “broken” by her death.
Police are investigating her death but it is not being treated as suspicious.
Sister Tesni, 24, said: “We are heartbroken to say that our beautiful Bronwen sadly passed away on Thursday, after fighting so very hard to battle with her mental health.
“For those of you who knew Bron, you’ll know she was the most beautiful, thoughtful, inspiring and loving person. We as a family are broken.
“We would like to say thank you to everyone who has sent their love and condolences, it is so warming to see how many lives Bronwen touched and how loved she was.
“Bronny, we will forever love you, thank you for being the greatest sister, daughter and friend.”
Friends paid tribute to amateur boxer Bronwen, who was described as having a “heart of gold”.
Katie Scott wrote: “Both a mental health nurse and a boxing champ, your talents saw no bounds, blessed with beauty, brains and bubbliness you really were the best around.
“We will treasure all our memories as our lives go on. And forever love and remember you, our beautiful Bron.”
Stacey Horne said: “I could tell you had a heart of gold. Such a kind and caring human who would have given her last penny to anyone in need.”
A police spokeswoman said: “South Wales Police is investigating the death of a 26-year-old woman who was taken ill at a hotel on Pentwyn Road, Cardiff, on Thursday, August 27.
“The woman was later declared deceased at the University Hospital of Wales.
“Her death is not being treated as suspicious and next of kin and HM Coroner have been informed.”
A spokeswoman for South Wales Central Coroner’s Office said an inquest into her death was due to be opened later this week.