According to this [0] she had moved to Rome in 1922. Unlike 9-11ers, she didn’t move to the country explicitly to perform the action; she likely grew to dislike Mussolini by spending time in the country. By that metric, I’d call it home-grown.
> In her room at the convent Gibson had amassed a collection of newspaper cuttings critical of Mussolini, and others outlining his movements. She also had a box of bullets. The origin of the revolver, her second, was never determined. The lead detective investigating the case believed Gibson was feigning madness and had not acted alone but possibly in collaboration with catholic modernist dissidents from the poor Trastevere neighbourhood. [...]
> In June 1926, succumbing to immense pressure, Gibson made a confession. Her story was that she had committed the crime to impress an Italian duke named Giovanni Colonna, who she had fallen in love with years before in Switzerland. Vehemently opposed to fascism, she claimed Colonna had communicated his desire for Mussolini's death through a series of clues before gifting her with gun and bullets, that led her to the assassination site that fateful day. The duke was under surveillance for anti-fascist activities, and his movements at the time of the shooting could not be accounted for, lending plausibility to Gibson's account.
Clearly this was not the work of a foreign faction, there was a clear element of Italian involvement.
Words placed into the mouth of a crazy woman (implicating an enemy of the people asking the questions) who was determined to kill -somebody- it’s mentioned elsewhere that she may have wanted to target the Pope.
[0] https://m.belfasttelegraph.co.uk/life/features/profile-viole...