I kind of don't understand why people are making cosplay suggestions for characters she might not even know exist, or even LIKE if she's introduced to the series. Personally, if I were going to a foreign country and someone told me to dress as the character America (or China, or England, or something else I already am) I'd be kind of offended. I don't care for the character, or the series, and even if I did I don't want to make a first impression by saying PLEASE, IDENTIFY ME SOLELY BY THIS COUNTRY I'M FROM.
If she wants to go, invite her to come, maybe wearing a nice dress or something formal and more fun than jeans and a t-shirt... But if I'm in a new country and already a little overwhelmed by adjusting to DAILY LIFE, the last thing I want is to be tacklehugged by strangers who are gross and saying how much they want to make out with my character. There are awkward people at cons every year every day etc etc, if you wanna introduce her to con life then don't accidentally make her a walking target for those select socially inept people.