Laois county councillor Caroline Dwane-Stanley, the wife of Independent TD Brian Stanley, has resigned from Sinn Féin.
Councillor Dwane-Stanley said she had given the decision "careful consideration and reflection".
She cited the controversy in July surrounding her husband and related matters since which she claimed included "outright attacks" on her personally and on her family.
Brian Stanley left Sinn Féin in October, saying he had been subjected to a seriously flawed complaints process which he likened to a kangaroo court.
Ms Dwane-Stanley was Sinn Féin's only councillor on Laois County Council after Councillor Aidan Mullins resigned from the party in August.
In October, she was appointed to an EU committee for local representatives.
The Committee of the Regions is a consultative body representing local and regional government at EU level.
In a statement, she said the "time is now right to draw a line on 2024 and resign".
"I will continue in my role as an independent republican councillor providing vigorous and effective representation for the Portlaoise/Abbeyleix Municipal District" she said.
Councillor Dwayne-Stanley has been a member of Laois County Council for more than 10 years.
