Your girlfriend sounds sensible and fun. (Like a Skoda vRS

).
There are two accredited courses, TESOL and CELTA. Slightly different in approaches, but both widely recognized the world over. A "proper" course can be completed in intensive fashion in 4/5 weeks and includes live teaching practice. On average they cost around 2-2.5k of whatever currency you pay in and they can be completed in many different countries.
As a fan of Spanish speaking places, I investigated Ecuador, Mexico, Majorca and the mainland. The market in Latin America is booming. Especially in Brazil and Central America. She could be on to a winner. If I wasn't doing well at what I'm doing now, I would consider it (in fact, I may still consider it)
Try CactusTEFL as a starting point for info. When looking for courses, use the official approved course lists from Cambridge and the TESOL people.