Currency trading is not easy to figure out because it's not like stocks where you just need a successful business trading for a reasonable price. Currency movements depend on government actions and the competitiveness of a country's industries with other countries:
1. Not all currencies will mean revert to where they traded vs other currencies,
2. Sometimes, the reversion won't occur for many years - too many to be of practical use
3. You likely have no special insight into which country will enact a liberal monetary policy and which country will enact austere measures
I bought a One Billion Dollars Zimbabwe bill, and it came with a free One Dollar Bill. I tell myself I have it as a reminder that inflation matters, but really it's just a cool novelty. The One Billion Dollars note was worth $400 US dollars at the beginning of 2014, and less than a US cent at the end. Zimbabwe is one of the few countries to experience such inflation without a total system collapse leading to war.
It's hard to look at South America as one market, and mostly unfair to group all their countries together as being unstable politically. If your partner's money is in Venezuela, get it out now! You probably already know that already - Venezuelan citizens have taken to using adjacent country currencies and even Gold shavings to continue buying things. Chile has been very stable politically and economically for at least 3 decades, but Chilean companies are small. Argentina tends to boom/bust with inflation and foreign investments, and Brazil is the juggernaut in the continent, attracting foreign investments and emerging market ETF money.
It reads as if your partner has citizenship, but if not, you should familiarize yourself with any travel or visa benefits to keeping money in this South American country. I'm not sure I would suggest you invest in companies in your partner's home country - many will be smaller than global companies based in Europe or the US, and brokerages and funds are likely to have higher fees.
