Tweed proposed to Goody last Friday and the pair plan to marry at the Victorian Chapel in the Royal Marsden Hospital, The Sun reports.
Goody said: "I swear we will be a family before I die - just not for as long as I’d hoped. I love Jack with all my heart and want to be his wife more than anything in the world. And I will be.
"All I want to do is spend whatever time I have left with him and the kids."
A friend added: "Jade is dying - she knows that. But this wedding has given her something to look forward to, and she's decided to just get on with it.
"It's now everything to her. She desperately wants Jack as her husband before the end - it's all she has left."
Goody was seen visiting an Armani store in Knightsbridge at the weekend as she shopped for a wedding dress with Tweed and his mother, Mary.
It was previously reported that the Big Brother star could sign a deal worth £1 million for the media rights to cover her wedding.