The actress-and-singer's millionaire property developer boyfriend Nick Candy popped the question by going down on one knee in front of a sign with the words 'Will you marry me?' blazing in lights and Holly revealed she was quick to accept.
Posting a picture of the romantic moment on twitter, she wrote: "And I said YES!!! Happiest day of my life!!!!! Xxxx (sic)"
Holly recently revealed the secret to her lasting relationship with Nick is that they are first and foremost best friends.
She said: "Nick's got to be the funniest person I've ever met in my life - he's hysterical. We're like two kids running around London all the time, giggling in the back of taxis. I do love being around him. We're great mates.
"When we first met, I didn't know anything about him. I just thought 'Cor, if I didn't fancy you so much, we'd be the best of friends. Instead, I just want to make out with you all the time'."
When she did learn about his wealth, Holly "freaked out".
"I rang my mum and said: 'I don't think I can do this because it's just too much.
"And she said: 'You can't hold that against the man. He's a hard-working genius and he's got as much right as anyone else to love and be loved. So you just stop looking at his bespoke chandelier and his gorgeous car and start thinking about him'."
Before she started dating Nick, Holly had a long-term relationship with 'Hawaii Five-0' star Alex O' Loughlin, which ended in 2009.