However, in spite of this terminal diagnosis Ms Truman was given a new lease on life when she fell pregnant in March, 2016.
Ms Truman said she was offered treatment to help slow down the cancer but refused it to protect the health of her baby.
"I wasn't planning on getting pregnant but it just happened. I wasn't going to let my cancer affect having a child, because he was my all."
Now three and a half months old, Daeshaun is her "world" and has given her a remarkable perspective on the limited time she has left.
"When I'm stressed I always talk to him, even though he can't talk back to me. He's given me hope. It's really indescribable you can't really explain how they make you feel because it's like to infinity and back. It's just an amazing feeling."
She had been keeping a memory box, filling it with notes and letters for her son to read in the future.
"I write a letter to him every day. Every day since he's been born I've written something about him, or something we've done that day."
A Givealittle page has been set up to help her create lasting experiences and memories for her baby boy.
When asked what she wanted to do with the money donated she said she wanted to take Daeshaun to her favourite place, the Bay of Islands.
"I want to take him to the places I love."
Despite admitting to sleepless nights her fear of dying has transformed into an acceptance that death is something that will happen.
"I just carry on normally I guess. Sometimes you've just got to fake that smile, but that's the only way you get through things sometimes."
"I think if you have a positive mind you have positive outcomes."
Those wishing to donate to Rhianna can visit www.givealittle.co.nz/cause/rhiannaanddaeshaunsjourney