Does it cost money to use imessage with someone in a different country?

I live in the USA and my friend lives in Canada. She just got an iphone and i have one as well so i was wondering if it would cost extra money to use imessage considering she's in a different country or would i be free of extra charges? I understand that I would be charged extra if it was via text but does the same thing apply for imessage?

Dude just download a free texting app. If you have unlimited data that is or if you just use internet when connected to Wi-Fi
Here are a few
Viber
Tango
Pinger
Those are the ones mainly used i believe

No its completely free, it will only cost you if say your internet goes down for some odd reason and it needs to send as a normal text it may automatically do so (the message will turn green instead of usual blue, imessage also relies on the internet if you didn't know). Go into settings > messages > and turn off 'send as sms" which will prevent your iPhone from sending imessages as texts automatically if say there's ever an internet connectivity problem. You can still contact other people without imessage after turning that off, it only applies to your imessage contacts.