Speaking to BBC Sport before the Games, Petrillo, who transitioned in 2019, said her participation in Paris would be an “important symbol of inclusion”.
After Monday’s heat, she added: “The atmosphere in the stadium is great, it’s just a dream come true.
“From today I don’t want to hear anything more about discrimination, prejudices against transgender people.”
Currently, there is no unified position in sport towards transgender inclusion.
The International Paralympic Committee (IPC) allows international sport governing bodies to set their own policies.
IPC president Andrew Parsons told BBC Sport that, while Petrillo would be “welcome” in Paris under current World Para Athletics policies, he wants to see the sporting world “unite” on its transgender policies.
It had been reported Petrillo was the first openly transgender athlete to compete at the Paralympics.
But the IPC has since told the BBC Dutch transgender athlete Ingrid van Kranen, who died in 2021, finished ninth in the women’s discus final at the Rio 2016 Games.
Van Kranen’s story was not widely known at the time.
Mariuccia Quilleri, a lawyer and athlete who has represented a number of fellow athletes who opposed Petrillo’s participation in women’s races, said inclusion had been chosen over fairness and “there is not much more we can do”.
Tokyo 2020 silver medallist Ukraine Oksana Boturchuk, who reached Tuesday’s final, said: “I find this not fair, in my opinion. I am not against transgenders in general but in this situation I do not understand and don’t support it.”
Venezuela’s Paralympic Committee (VPC) has called it a “a terrible inequality that puts female athletes (born female) at a great disadvantage”.
General secretary Johan Marin told BBC Sport: “We are completely against discrimination, inequality and/or exclusion of any person or group in any social sphere.
“Therefore, respect for individual rights, inclusion and equality must always prevail.”
Marin called for an open category for transgender athletes to compete in, calling it the “fairest and most sensible thing”.