"The girls approached me and said they were getting together to do a world tour, a greatest hits album and a big goodbye, and I was like: 'Oh no.' It was the last thing I wanted to hear," the 33-year-old told Closer magazine.
"All four of them had spoken about it and it was set in stone. They basically said if I wanted to do it, great, but if I didn't want to do it then they were going to do it anyway. So I was like: 'Wow, what do I do?'
"I always said I'd never do it. But I didn't want to miss out and have regrets. I also didn't want to be the person that stopped it being the complete five – I was scared I'd be the villain. It was hard, so I didn't say yes immediately.
"I changed my mind every day – it was difficult."
And she admitted: "The thought of singing 'Wannabe' makes me cringe. But I know I'll love doing it once we get going."
