Debbie had initially refused Marc's marriage proposal because she feared she had cancer. But after receiving the all-clear from her doctor, she has decided to accept.
In an phone interview with TMZ this week, the mum-of-two revealed she had turned Marc down three weeks ago because of uncertainty about her health.
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"I had gone into the hospital before and they were worried about cancer," she revealed. "And I didn't feel like I could say 'yes' knowing that."
On Wednesday, Debbie was told that she has sarcoidosis — an auto-immune disease that is not life-threatening.
"The doctor said 'You're good to go'. I drove up to the house and I said, 'OK, I'm here, and I'm going to be here for a while, so I'm going to marry you," she said.
Debbie and Marc have known each other for many years, and love blossomed for the couple in the years following her divorce from the King of Pop — the pair were married from 1996 until 1999.
"We just remained friends," Debbie said. "He helped me with a lot of things and friendship sometimes turns into relationships and that's what happened.
Debbie is mum to two children from her marriage to Michael — Prince, 17, and daughter Paris, 16 — and they have also given her relationship their approval. "The kids have known him (Marc) since they were little and they like him a lot," she said.
"We haven't set a date yet," she added. "You know, I'm happy with the way things are, it takes me a little while to get used to things."