"Brooke had to have emergency surgery to have her wisdom tooth extracted (Tuesday,)" Mueller's mother, Moira Fiore, told E! News exclusively Wednesday. "It became infected. The infection spread and now she has pneumonia in both lungs."
"Brooke is still in the hospital. She's doing OK but she's not doing great," added Mueller's lawyer, Yale Galanter. "We thought there was a possibility she was going to be released today, but she's not because she has developed pneumonia in her lungs."
Mueller and Sheen were ordered by a Colorado judge to stay away from each other following Sheen's Dec. 25 arrest for allegedly threatening and assaulting her. However, the couple, who have 10-month-old twin sons together, reportedly want to be back together.
A judge Wednesday approved Galanter's request to allow Sheen to visit his wife in the hospital, which the actor has since done, E! News said.
The couple reportedly had been scheduled to appear in court Wednesday to discuss the Christmas Day incident, but the hearing was canceled due to Mueller's illness.
Galanter said he requested the hearing be rescheduled for Feb. 8.