SERAP says Mrs Jonathan or anybody for that matter can never stop it from carrying out its mandates.
She alleges that the non-governmental organisation embarked on a 'campaign of calumny' against her person.
The suit was filed before a Federal High Court sitting in Lagos, through a youth organisation - 'Union of Niger Delta Youth Organization for Equity, Justice and Good Governance.'
The organisation, according to the suit, is suing for itself and on behalf of Mrs Jonathan.
It accused SERAP of making use of the online, print and electronic media to publish unfounded and malicious allegations against the ex-first lady that she stole $15 million.
Reacting to the suit, SERAP says it is ready for the legal battle against the ex-first lady.
In a statement issued on Thursday, October 20, by the Executive Director of SERAP, Adetokunbo Mumuni, the group described the move against it as intimidation and harassment.
"SERAP will never, in the discharge of its mandates, succumb to any intimidation, harassment and attacks in any way, shape or form," the statement said.
SERAP had repeatedly demanded the Federal Government to prosecute Mrs Jonathan following the revelation by the Economic and Financial Crimes Commission (EFCC) that large sums of money stashed in various bank accounts, amounting to $15 million, were traced to her.
The human rights advocacy group even went further to sue the government for failing to initiate criminal charges against the ex-first lady over the funds believed to have been acquired fraudulently.
But the youth group representing Mrs Jonathan claimed she acquired the $15 million legitimately - it was said to be an accumulation of gifts from her friends and well-wishers over the last 15 years.
"She had been saving in order to utilise to upgrade family businesses and concerns which had been somewhat dormant by reason of the long period of her husband service as a public officer in Nigeria," the group said in a previous statement.
The ex-First Lady had also claimed, in a suit against the EFCC in which she demanded the release of her frozen bank accounts, that some of the funds were meant for her medical bill.