Ms Guy also laughed off the rumour Macdonald was having a gay affair and her brother had threatened to expose it.
"You know, anything's possible, but no - they just get more and more ridiculous really.''
Ms Guy has spoken in the past about her frustration with rumours about her new relationship, but candidly told 60 Minutes the man she was now seeing was "very special''.
She said the relationship had started only recently and it was "early days''.
"I really was not thinking about men when Ewen was arrested - I was focused on the kids, and you know at the end of the day, they're my first priority.''
Ms Guy said she and Macdonald were still friendly but the relationship was distant.
Macdonald was sentenced earlier this month to five years in prison for six unrelated charges, including burning down a home on Mr Guy's property and vandalising another property Scott and Kylee were having built.
"He can ring and talk to the kids. It's OK - it's quite distant though. We don't want to get nasty at each other and bitter, because the only people that will suffer is the kids.''
Ms Guy said her four children with Macdonald could decide for themselves what kind of relationship they wanted with him when they got older.
"It's not really my place to make a decision. If they want to go and see him, they can - I would never say you can't go and see them.''
Ms Guy said she was starting a whole new chapter in her life and was hoping to move to Auckland to start a new career.
She also spoke of the heartbreak upon finding out Macdonald had been charged with her brother's murder.
"I just remember my heart sinking, and it was just such an awful feeling that the person that I married and had known for so long was not the person I thought I knew. He had secrets.''
Ms Guy said a lot of people had asked her how she did not know about the other crimes her husband had committed - including his night-time "missions'' to kill calves, poach deer and commit vandalism and arson.
"I think a lot of people don't have four kids under five, either, and I didn't sleep a lot for a good five years, and it was probably a bit zombie-like.
"I think Ewen and I did led separate lives a little. We were great flatmates and great as a team, we both helped out with the kids. But we were more separate, rather than together.''
Speaking about the decision to leave Macdonald, Ms Guy said it was upsetting to let a friend go.
"But the things he did, it makes it at easy decision. It just doesn't seem like the person I married and I don't really want anything to do with that.''
Ms Guy said taking to the stand at his murder trial was "probably the worst thing I have ever done in my life''.
"It's just really hard to go back and think about that because every day I just try to not think about it, because it is such an awful thing to go through.''
Asked whether she agreed with the jury's decision, Ms Guy said they had sat through all the evidence, not her - but there were still so many unanswered questions.
"I just don't know.''
