The former EastEnders star has exclusively told Daily Star Online that she feels like she is "back to square one" with her drugs battle.
She said: "I have relapsed and I'm trying to stop using, but it's a long road ahead.
"I feel broken and that I'm back to square one and my first form of defence is cocaine."
Danniella's admission comes as she claimed today her 24-year-old boyfriend George Arnold has cheated on her.
The star made the shocking allegations on Instagram in posts that she has now deleted.
She shared a post with her 103,000 followers which read: "Don't do wifey s*** for a f*** boy."
Danniella captioned the picture: "Word to the women who bump into George Arnold. I just found out he's been screwing my best friend.
"They even went to Ibiza together last weekend."
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The Sun claimed that George hit back on one of Danniella's posts, writing: "No truth in this at all, there’s two sides to a coin before all you believe what you read."
Danniella's struggle with drugs has been well-documented over the years.
She confessed in the past that she tried her first drug at the age of 14.
After winning her role on EastEnders at the age of 16, she was a regular on the party scene and admitted that she was easily led into drugs.
The most famous incident with drugs Daniella has been involved in was when she was picturing at the British Soap Awards in May 2000 with her septum missing, unveiling the extent of her excessive drug use.
She was then checked into rehab and six months later appeared on Channel 4 show The Priory, claiming that she had been free from drugs for some months.
Danniella's last relapse was in 2014, when she admitted she turned to drugs when life got hard.
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She also shared her drugs battle in a Channel 5 documentary earlier this year, titled Daniella Westbrook: In Therapy, which she said "changed her life".
Those who may need help with any drug-related issues can contract Samaritans free helpline on 116 123.