Under the terms of her child custody agreement with Sheen, Mueller is required to undergo drug testing three times per month but she apparently refused to take part last Friday when conductors arrived at her home.
A source has now told TMZ that Mueller has decided to seek professional treatment by checking into rehab.
The move comes just one day ahead of a plan by Sheen's attorneys to take up Mueller's refusal to submit to drug testing in court on Tuesday.
Mueller and Sheen were married for just two years, before filing for divorce last November.
They are parents to twin sons Bob and Max, whom Mueller had removed from Sheen's home in March after the former Two and a Half Men star began giving a series of candid interviews to the media.
Sheen made headlines late last week when he claimed during his tour stop in Toronto that he might return to Two and a Half Men.