Patricia Alejandra Lorenzo Harris travelled from Rawson to Blaenau Ffestiniog, Gwynedd. a year after the towns were twinned to mark 150 years since the migration.
She said it was a "dream" to visit her great-grandfather's home country.
Next year a grant will allow someone from the town to visit Rawson.
The first Welsh settlers to reach Patagonia founded Rawson, which is the capital of the Province of Chubut.
Among the nearly 200 settlers who sailed south on the Mimosa in 1865, at least five were from Blaenau Ffestiniog, and the towns were twinned last year to help re-establish the link.
Historian Ms Harris, president of the twinning commission, travelled with her friend Marisa Conde to learn more about where her ancestors came from.
They visited the Welsh Highland Railway, Llechwedd Slate Caverns, took part in a Spanish lesson at Aberystwyth University and visited Ysgol Maenofferen where they presented gifts from children of 178 Suyay Hue School in Rawson.
Ms Harris said: "It's been my dream to come to Wales and see the country. When I was young, I spent a lot of time speaking to my grandfather and he told me about how his father had travelled from Wales with his family.
"I also feel a great responsibility to bring greetings from the whole of the community in Rawson and to re-establish the link between between Rawson and Ffestiniog."

It has been launched by the association that represents thousands of officers.
The Police Federation said officers took 37,674 days off sick last year because of the problem.
Federation chairman Mark Lindsay described the resources the PSNI devotes to tackling the issue as "pitiful and wholly inaccurate"
In his speech to the association's annual conference in Belfast, he described the current situation within the police as "a professional scandal".
"This problem needs this urgent intervention," he said.
"Whole families are suffering because those hurting are falling through the cracks."
He said the fund announced on Wednesday would be used during the next three years to provide additional therapists and psychologists dealing with the issue.
Mr Lindsay said the fund was a temporary measure, and that it was the "statutory duty" of the Police Service of Northern Ireland and Department of Justice to address the problem.
Last week, three officers who have been treated for post traumatic stress disorder PTSD spoke to the BBC about their experiences, and problems getting treatment.

Mladen Grujicic, who acknowledges the killings took place, won 54.4% of the vote, triggering alarm and calls for a recount among the Muslim population.
Srebrenica was a Muslim-majority town before the war, but is now 55% Serb and 45% Bosniak (Muslim).
The July 1995 slaughter has been deemed genocide by two international courts.
Speaking to AFP before the vote, Mr Grujicic said "the crime against the Muslims took place" but like most Serbs refused to recognise it as genocide, saying: "I leave (it to) competent institutions to qualify it."
Outgoing Muslim mayor Camil Durakovic refused to concede defeat, crying foul and pledging to lodge a complaint.
But Bosnian Serb leader Milorad Dodik said their candidate won, adding that chemistry teacher Mr Grujicic would lead a  politics of "reality in Srebrenica" and would respect everyone, Beta news agency reported.
Hatidza Mehmedovic, who lost her husband and two sons and heads a survivors' organisation, said Mr Grujicic "could not run" the town "because his idols are war criminals such as Radovan Karadzic", the Serbs' political leader during Bosnia's brutal 1992-1995 civil war who is serving a 40-year jail term.
"I do not fear for myself. They killed me a long time ago with my sons," she added.
"But I do fear for the young ones who have children and who are trying to rebuild something in Srebrenica, first of all trust."
A descendant of two of the first people from Wales to resettle in Argentina's Patagonia has visited the north Wales town where her relatives came from.
[NEXT_CONCEPT]
A £1m fund has been set up to help police officers suffering from post traumatic stress disorder and other psychological illnesses.
[NEXT_CONCEPT]
A man accused of not recognising the murders of 8,000 Muslim men and boys in Srebrenica as genocide has been elected the town's first Serb mayor since 1999.