BOSTON • A South Korean woman who allegedly incited her college boyfriend's suicide in a parking garage in Boston told the authorities that she rushed there to try to stop him, according to local media reports.

This was revealed on Tuesday, even as prosecutors stood by their decision to indict her.

Inyoung You, 21, was indicted on Monday for involuntary manslaughter over the death of her boyfriend Alexander Urtula in May. The Boston College student killed himself just hours before his graduation.

Prosecutors described You as an abusive woman who had full control over her 22-year-old boyfriend.

She allegedly took advantage of his depression to isolate him from his family and friends, as she abused him verbally, mentally and physically over 18 months.

She allegedly sent him more than 47,000 messages in the two months before his death, urging him hundreds of times to kill himself and telling him the world would be better off without him.

You, who withdrew from Boston College in August and returned to South Korea, was deemed to have displayed "wanton and reckless" behaviour and "created life-threatening conditions" for her boyfriend.

A more complete summary of the facts and events before and after Mr Urtula's death will be revealed in due course, said Suffolk District Attorney Rachael Rollins.

"I stand firmly behind this office's detailed presentation of the evidence to the Suffolk County grand jury and the returned indictment against Ms You," she was cited as saying by the Boston Globe.

The authorities are preparing to seek You's extradition from South Korea and are "cautiously optimistic" over her cooperation. The two countries share an extradition treaty that goes back to 1999.

But legal experts have warned of potential obstacles, citing differing views towards the incitement of suicide as a punishable offence.

In Massachusetts, Michelle Carter was the first to be convicted of manslaughter in 2015 for encouraging her long-distance boyfriend to end his life.

South Korea's Criminal Act states that a person who instigates or aids and abets another to commit suicide could be jailed for up to 10 years. But the execution of this law has been rather lenient, even as the country struggles with high suicide rates.

International law professor John Cerone has warned that South Korea might not agree with the US' reasons for You's indictment and "might argue that the mode of participation in the crime would not be recognised under South Korean law".

Tufts international law professor Hurst Hannum added that it is "conceivable that South Korea could have an entirely different approach to the crime".

Meanwhile, some anecdotes have emerged of You. Local reports said she grew up in Issaquah, east of Seattle, and graduated from high school with good results. She was also an avid tennis player.

A Boston College student said You confided in him about her relationship problems, and that it was difficult for her. He also described her as a funny and caring woman who seemed genuinely interested in helping other people.

"She was a very kind person," he said. "When you talked to her, she would never seem like the type of person to say these kinds of things... I couldn't believe that she would have done this."

The shocking case has grabbed newspaper headlines and gone viral online. But in South Korea, where You is said to be residing, there is little media coverage and the story did not generate much online chatter.

It remains to be seen whether she will return to the US to face charges.