Gia's boyfriend Ryan Anderson found her hanging and unconscious in her home on Monday and immediately called 911, reported TMZ.
The model, who appeared on season 14 of the hit reality series, was taken to University Hospital in New Orleans and she breathed her last yesterday.
Report said that the brunette was placed on life support and had her mother and her longtime boyfriend by her side.
Anderson has released a statement saying, "I'm deeply grateful for all the love and support we have received from family, friends and fans. Gia was the most beautiful person I knew inside and out and she always smiled and made everyone else around her smile.
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Former 'Bachelor' star Sean Lowe tweeted about the tragic news.
"My prayers go out to Gia Allemand's family during this time. Life on earth is but a vapor and she's with our Lord now," she wrote.
Season 14 winner Vienna Girardi said, "Gia was a beautiful girl and an unbelievable friend. I'm shocked and can't believe what happened to her. She seemed so happy, but you never know the demons people are fighting inside. I will never forget her and will miss my friend forever.