The actress and presenter, who is one of Matalan's brand ambassadors, visited the shop in Walsall to present customer Christine Wilkes with a new Fiat 500.
Christine, from Walsall, was automatically entered into the prize draw after using her Matalan Reward Card in store.
She said: "I couldn't believe it when Matalan contacted me to tell me I had won a brand new car.
"I am a regular Matalan customer and always swipe my Reward Card, but I never in a million years thought that I would be the star prize winner.
"It has been brilliant meeting Denise and the Matalan team, the icing on the cake."
Denise said: "It has been so much fun meeting Christine and her family today, as well as the amazing staff and customers at Matalan's Walsall store.
"What an incredible prize, I hope Christine enjoys her lovely new car."
Jan Chapman, Matalan Walsall North store manager, added: "We are so excited that the star prize Reward Card winner is a Walsall North shopper. Not only that, but this is the biggest prize that Matalan has had up for grabs so far, so this is truly extra special.
"We had another Reward Card winner at the store a few years ago, so I definitely think this is a lucky store.
"I hope Christine enjoys her prize and I look forward to seeing her and her family in store again soon.”
Matalan customers are automatically entered into the prize draw as soon as they shop at Matalan and use their Reward Card. Prizes are on offer each month, from a £5 gift card to a star prize worth between £500 to £10,000.
The Fiat 500 is the biggest prize to be won so far as part of the Matalan Reward Card programme.