Brooke Mueller is back in rehab after a 4-day drug binge with her ex-husband Charlie Sheen.

ā€œShe met up with Charlie again, partied for four days straight at his Mulholland Estate home and ultimately fell off the wagon,ā€ an unnamed source told the Celebuzz.

Her spokesman Steve Honig said she's taking it day by day.

"She will spend the rest of her life trying to stay sober, with every day being a struggle,ā€ he said. "As part of her ongoing treatment and as planned, she voluntarily checked herself into a rehab facility several weeks ago. Brooke is doing well and is grateful she has a strong support system on which she can rely.ā€

In early December, Muelller was busted in Aspen, CO. with four grams of cocaine on her person. She spent three months in rehab following that arrest and is now on probation. Testing positive for drug use can potentially send her to jail.

[NY Daily News]