Unable to send Korean text to other devices

[AC Question]

Hello, I am using a Samsung Note 2, I am unable to send Korean text to my girlfriend's Iphone4s. She is able to receive Korean text from both her sister (who has an iphone as well), and her mother who has a Galaxy S4. I have tried 2 different keyboards, but with no luck.

I am able to see the Korean text on my phone, but it displays on her phone as a series of question marks.