There is no problem to have multiple languages. I work with the players to discuss how they envision the character. I don't go into dialects of a language, as it gets too much detailed and we find it unnecessary, but we decide based on the backstory what kind of language points must be spend so the character looks appropriate.
For example, I had player that wanted to play french professor (lived his early twenties in France) that moved to USA. I asked him to use French as Language Own skill and because of the story and the way he wanted to play to put the necessary Skill points into Language - English. This makes a lot of sense as this is often what people must do when they are expats - learn the new language if different.
In your case because of the story, you should ask the player to invest personal or occupational skill points (if available) to the extra languages. In the rulebook there is table that shows what points you need to be flient, native and etc.