Ms Elder-Holmes, daughter of late broadcaster Sir Paul Holmes, will today be announced as one of the main attractions of December's KFC Fight For Life boxing promotion in Hamilton.
Duco Events director David Higgins said Ms Elder-Holmes had indicated she would dedicate her bout to Mr Morris' memory.
Mr Morris, a member of the Head Hunters gang, died after a confrontation outside a West Auckland party on August 3. Ms Elder-Holmes held her partner of six years as he lay dying.
This morning Ms Elder-Holmes confirmed on Instagram that she was taking part, saying Fight For Life supported Hospice, which had looked after her late father very well in his last days.
She and Mr Morris has spoken about it many times and he had loved the idea but personal reasons had held her back.
"I'm doing it to challenge and focus myself and to make Connor proud.
"I have the full support [of] our family and friends, yes I realise this puts me in the public eye but everything I do or that happens to me seems to end up in the public eye so why let that hold me back," she said.
Mr Higgins denied his company was looking to cash in on the publicity surrounding Ms Elder-Holmes following Mr Morris' death.
"We've actually been talking to her for a couple of years about doing it so this is nothing new or opportunistic," he said. "We've kept in touch, she was keen to do it one day and she has obviously decided that the timing is right for her.
"We wouldn't go into this lightly. We met her two or three times and had a good talk about it. She is an adult making a decision to take on a challenge. Is it really that different to running a marathon?
"There are definitely some positives here and I think it could be good for Millie."
Ms Elder-Holmes has avoided the media since Mr Morris' death. However as a Fight For Life contestant she will be very much in the public eye. Mr Higgins was confident Ms Elder-Holmes would meet her obligations, which were to begin with a press conference today.
"Think back to [former contestant] Jesse Ryder -- he was out of reach a bit then signed on to do the fight and fronted up really well," Mr Higgins said.
"I think he found it beneficial. I don't really see a negative about it. It's a challenge and something to focus on. It gets you fit and those that have done it have said it is a lot of fun. The fighters all get paid a fee. There is no loser in this."
An opponent has not been confirmed for Ms Elder-Holmes, however it will not be Mona Dotcom, the wife of internet tycoon Kim Dotcom, who was recently linked to the promotion. Mrs Dotcom is considered too small to fight Ms Elder-Holmes. Duco has instead called for expressions of interest, preferably from celebrities looking to get in the ring.
Mr Morris had a keen interest in fight sports. Shortly before his death he was pictured with Kiwi mixed martial arts stars Mark Hunt and James Te Huna and his tangi was held at the Head Hunters' Fight Club 88 gym. The 33-year-old man accused of murdering him will stand trial next year.
By Steve Deane and James Ihaka of the New Zealand Herald
