The sparkler in question, thought to be a five-carat diamond and described by Mark as a "monster rock", is still at the jewellers waiting to be resized.
"Cant wait 2get my ring back nxt week after its been adjusted, so many people askin 2 see it,n I have 2 show them a bare hand! #skinnyfingers," tweeted Michelle.
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The Coronation Street actress was the special guest of honour at the launch of Sally's on Oxford Street, as she opened the store on Thursday morning.
The bare-handed Michelle cut the pink ribbon using a giant pair of scissors, much to the delight and applause of crowds. The brunette beauty, who is known for her on-trend fashion sense, looked chic in a classic white top and navy cigarette trousers.
Sources close to Mark and Michelle confirmed that the TOWIE favourite proposed during a romantic holiday in Dubai, the exotic location where the lovebirds first got together nine months ago.
Michelle excitedly tweeted the news on Monday, writing, "THANK YOU for all the lovely messages, and yes it's true @markwright_ and I are engaged!! We are so SO happy :-) xxx."
The couple – both 26 – are said to be "blissfully happy" after Mark's proposal, which took Michelle completely by surprise.
Michelle was previously engaged to The Wanted singer Max George, but she called off the engagement in July 2012 after claims surfaced that Max had been unfaithful.
The 25-year-old singer, who was asked how he felt about his ex-fiancé's news in an interview on Daybreak, clearly has no hard feelings towards the lovebirds.
"I'm actually really happy for her, she's a wonderful girl," said Max. "I've met Mark and he seems like a really nice bloke so yeah - I wish them all the luck in the world."