One of Butler's research interests is the geneticdifference between pathogenic and non-pathogenic Candida species. In 2009, she co-authored a paper in Nature reporting genome sequences of six Candida species and discussing differences between pathogenic and non-pathogenic species.
Research funding
Butler was one of the signatories of a 2012 letter to The Irish Times from several scientists about the Irish Government funding applied science at the expense of basic science. Butler said that "a lot of us will not have access to funds", and "I am one of the people considering whether I will have to leave Ireland."