Tuesday night, Richards, the mother of two of Sheen's daughters, who were staying with her at the Plaza, told Joy Behar that she knew the details of what happened in his hotel room but declined to disclose them.
Richards said during an interview on "The Joy Behar Show" that she "did help him at the hospital" after the incident but did not want to say what she knew out of concern for her relationship with Sheen and the welfare of their daughters, Sam, 6, and Lola, 5.
"They're at an age when they can start to understand," Richards told Behar. "They have no idea what went on and ... our stuff happened when they were much younger, which I'm so grateful for. We're in an amazing place. We've been getting along great for the last year, year and a half.
"As far as that situation, I'm trying to protect the girls from it as much as possible," Richards said.
"I'd rather leave that for Charlie to discuss," she added. "I do know what happened."
Sheen is about a week away from completing his probation stemming from his 2009 assault on his wife, Brooke Mueller, in which he allegedly threatened her with a knife. The Aspen District Attorney's office told TMZ.com that it's aware of the Plaza Hotel incident but won't take any action unless it receives facts showing that Sheen violated his probation.
In July, Sheen took time off from his hit television show voluntarily to enter a rehab facility -- for the third time in his career -- "as a preventive measure," according to his publicist.
At Sheen's sentencing in August, his attorney, Yale Galanter, said the actor had already spent 93 days at the Promises rehabilitation facility this year, and the center could choose to credit that time toward his sentence.
"Credit for time served is absolutely on the table," Galanter said. "How much credit he gets is up to Promises."
Galanter also said that Sheen and Mueller had been sober for months.
Substance abuse and anger issues aren't Sheen's only woes. Twice this year, cars stolen from his Hollywood Hills home have been found crashed and abandoned in a ravine.
ABC News' Rich Esposito and Sarah Netter contributed to this report.