Peter is expected to embark on a secret relationship with Carla Connor (Alison King) as his personal problems escalate in a forthcoming storyline.
However, Leanne has her own history of infidelity as she cheated on Peter with Nick Tilsley (Ben Price) late last year.
Asked whether Leanne could ever forgive Peter if she discovered the truth, Danson told TV Times: "I don't think she could not forgive him, because she's done the same thing. I'm assuming there'll be lots of rows and tears - again - if she finds out what's going on."
She continued: "Personally, I like them as a couple, even though they've not had many happy times. But I do think that to make any future happy times believable, they have to be apart for a considerable amount of time."
Meanwhile, Chris Gascoyne - who plays Peter - explained why his character finds himself drawn to Carla. The pair have often had heart-to-hearts due to their experiences with alcoholism.
"I think he's attracted to her, and I think there's a co-dependency there, whether they're drinking or not," Gascoyne said. "They understand each other perhaps on a different level that Peter and Leanne understand each other."
Coronation Street continues on Thursday night at 8pm on ITV1.
> Coronation Street Peter 'hits the bottle over Leanne'
> Coronation Street Peter Barlow scandal in store for Christmas
> Coronation Street star Chris Gascoyne reveals big Peter plans
> Coronation Street producer teases heartbreak plots
> Read more Coronation Street spoilers and news