An 86-year-old French widow arrested and detained by US immigration agents has been released and allowed to return to her home country.

Marie-Thérèse Ross-Mahé was arrested in her nightgown at the home she shared with her late husband, a retired US army captain, in Anniston, Alabama, more than two weeks ago. She had overstayed her 90-day visa, according to the US Department of Homeland Security.

She had moved 4,000 miles from her home in Brittany in north-west France to marry her former sweetheart William “Billy” Ross, whom she had met in the 1950s when she was a secretary working at a military base where he was stationed in France.

The French foreign minister, Jean-Noël Barrot, announced she had been released and flown back to France after Paris intervened in the case.

Her son – who wished to remain anonymous – told Ouest-France Newspaper: “Maman is finally free! It’s a huge relief.”

The New York Times reported that Ross-Mahé’s adult children met her at Charles-de-Gaulle airport in Paris on Friday morning, and that she was still dressed in her detention uniform of orange shoes, sweatpants and a grey sweater covered in stains and holes. One of her sons said she was in a state of shock and exhausted after her ordeal.

Ross-Mahé, from Nantes, married Ross in April last year, but a bitter inheritance battle erupted between her and Ross’s two sons after he died in January aged 85 without leaving a will, it was reported.

According to the New York Times, on 30 March Shirley Millwood, the county probate judge dealing with the inheritance dispute, issued an order temporarily banning Ross’s family from disposing of any of his assets. Under Alabama’s inheritance laws Ross-Mahé is entitled to half of Ross’s estate.

In a statement to the court, Ross-Mahé said she had missed an appointment with immigration officials to sort out her visa after her late husband’s eldest son, Gary, had redirected all mail sent to their home. She claimed one of his sons had cut off water, electricity and internet at the property.

On 1 April, two days after the order was issued, Ross-Mahé was arrested and taken to a federal immigration detention centre in Louisiana.

Millwood said she believed Ross’s youngest son, Tony, a retired Alabama state trooper, had misused his position as a government employee to tip off US Immigration and Customs Enforcement (ICE) that she had overstayed her visa. He has denied this.

Millwood has ordered Tony Ross and his older brother, Gary, to hand over the keys to their late father’s house and not remove any property from it.

Before her release from detention, Ross-Mahé’s son said the family had been extremely worried after she was “cuffed by the hands and feet like a dangerous criminal” during her arrest on 1 April, as she suffered from heart and back problems.

He said he, his brother and his sister had heard no news about their mother for a week after she was arrested, until French consular officials were allowed to visit her. On Wednesday, two weeks after her arrest, he said he spoke to his mother on the phone for the first time.

“She is in good spirits. She has been able to receive consular visits. She can see that people are looking out for her. She is able to look ahead to her future,” he told Ouest-France at the time. “She’s a fighter. She always impresses us.”

Ross-Mahé is among thousands of people targeted by the Trump administration’s mass deportation agenda, which has resulted in the spouses of US soldiers and military veterans detained.

Barrot told reporters on a visit to the southern city of Montpellier on Friday that Ross had “returned to France this morning and we are pleased about that”.