Her death at the Hospice Oncology, after a five-month battle with pancreatic cancer, was a major setback to hopes for action to name and prosecute the killer or killers of her brother Fabio.
Fabio Polenghi, her elder brother, was a Bangkok-based freelance photojournalist. He was shot dead in the morning of May 19, the last day of the Abhisit Vejjajiva government's dispersal operation against the red shirts near Sarasin intersection on Ratchadamri Road between Rama IV and Ratchaprasong.
Elisabetta Polenghi had been visiting Bangkok regularly ever since, to lay wreaths in memory of her brother and to push for investigation so that the truth of her brother's death could be told.
Herself a freelance artist and photographer, Elisabetta had knocked at every door possible from Lumpini police station to the Department of Special Investigation and the Justice Ministry, to try to move aside the red tape and fear among concerned agencies.
She had also showed up on the stages of the red shirt commemorations of the crackdown, and spoke in solidarity with relatives of other victims of the April-May, 2010, violence, as well as political prisoners and their families.
Polenghi had been determined to seek justice for her brother, one of the two foreign journalist killed during the troubles.
She attended almost every hearing of the inquest into the death of her brother until, on May 29 last year, the Southern Bangkok Criminal Court ruled that the photojournalist was killed by a bullet from the direction of the military forces. It stopped short of blaming the military, and said the court could not specify the shooter.
Though the family was satisfied overall with the ruling, the slow process of justice motivated Elisabetta to try to muscle through other channels. She sought to criminalise ex-prime minister Abhisit, his deputy and security minister Suthep Thaugsuban, and former army chief Anupong Paochinda. She said they should take responsibility for the fatal crackdown order.
She also pursued the case at the European Court of Human Rights.
Elisabetta also supported the move to bring her brother's killing to the International Criminal Court, though she was not a petitioner herself in the appeal to the ICC. A mother of a volunteer medic who was killed at Wat Pratumwanaram was the chief litigant at the ICC.
Polenghi had proposed during the past two years that Thai society should remember the death of her brother, not as a hero but as a reminder that in keeping democratic spirits alive, there were those who had to shed their lives and souls, among them Fabio.
The red shirt movement adopted Elisabetta as one of their "sisters in arms", but she made clear she had no intention of being a political pawn or tool. She simply sought to use all possible mechanisms to get justice.
Fabio and Elisabetta are survived by their parents, and by the eldest sister Arianna Polenghi, who confirmed the news of her sister's death.
The Foreign Correspondents' Club of Thailand issued a statement saying it is saddened to hear of her death.
Elisabetta "Polenghi was an indefatigable campaigner for a full investigation into the circumstances of her brother's death," the FCCT said. "She visited Thailand on a number of occasions to press the Thai authorities to hold those responsible for the more than 90 deaths during the 2010 turmoil accountable for their actions. Our thoughts are with the Polenghi family at this difficult time."