But that's exactly what they did.
"Believe it or not, we had dinner together with all of us," Richards -- who has two daughters, Sam, 5, and Lola, 3, with her ex -- tells E!'s Daily 10. "So I love that... It's important for our daughters to see us get along and to be able to be in the same room."
She adds: "I think anytime you go through a divorce it's such a huge change in your life, and obviously my divorce was very public and it got very nasty... Charlie and I didn't want that -- we didn't want all the conflict and this and that, and that's just was the situation was."
Their dinner even included 43-year-old Sheen's wife, Brooke Mueller, who gave birth to twin boys in March.
"Brooke and I have always gotten along, so obviously when we went through what we were all going through it was what it was. But I think she's great with my girls. They love her."
She adds that she and Sheen -- who divorced in November 2006 after five years of marriage -- have managed to put their troubles behind them.
"We've worked very hard to get it to this place, and I'm so grateful for it," the reality star says. "I think it's important for, you know... It's a lot less stress, it's a lot less money, that we get along."
How was she able to move past their long-standing feud?
"I don't have a choice but to get past it," she says. "You know, I don't read a lot of that stuff obviously -- I'm not stupid. I know what's said in most of it, but it's just moving forward in my life and at that time when it was really bad in my life, I didn't think about that stuff. I had to think about, 'I'm a Mom, I have two daughters that depend on me.' So I put all that stuff aside and I kind of just live in a little bubble."
Richards, 38, continues: "I like things very calm and happy."
The Daily 10 interview with Richards airs Friday at 7:30 p.m. EST.