Sarah Harding "cried hysterically" on her way to rehab.
The Girls Aloud singer felt "ashamed" and "embarrassed" about visiting a US treatment centre in October to seek help for depression and alcoholism, but it was her bandmates who first made her realise she had a problem.
She said: "The day I left for rehab, I was in such a mess. I've been told by those close to me that was when I hit my worst.
"I was crying hysterically. I felt ashamed, embarrassed, terrified - my emotions were all over the place."
Speaking about seeing her bandmates Nicola Roberts and Kimberley Walsh for dinner after a drunken previous night, she added: "I saw Nicola and Kimberley for dinner. I wasn't in a good state at all - I was very hungover. But the first thing I wanted to do was open a bottle of wine. I know they were really worried about me."
The blonde beauty's drinking escalated out of control when her relationship with former fiance Tom Crane began to take a turn for the worse.
She explained to Britain's HELLO! magazine: "Our lives had started to go in different directions without us even realising and we'd become like passing ships.
"He had his career, I had mine, and somehow they didn't seem to marry up. As far as our future plans were concerned, I didn't see how it would work.
"I was so down but I just tried to keep busy and, to numb myself, I was drinking more. It was my way of escaping."
Sarah – who checked out of rehab last month – believes she has turned her life around and is confident she can cope in social situations without alcohol.
She explained: "I’ve turned 30 now and, although there will always be a bit of the rock chick in me, I’m trying to embrace my softer and more feminine side. I’ve realised I can socialise without booze."