At least on the Web (Twitter, Instagram, and Google), these words are used in place of 오빠:
- oppa (English)
- オッパ (Japanese)
- โอปป้า (Thai)
- 欧巴 (Chinese)
All of them sound almost the same as 오빠. I am quite certain that you heard her saying 欧巴 because 哥哥 (gēge) sounds totally different from 欧巴 (ōubā).
In fact, 오빠 is in the lyrics of Gangnam Style and its video has now over three billion views on YouTube. This suggests that a lot of Internet users around the world know or hear the word, 오빠 as in 오빤.
Not only K-pop music but also K-dramas are popular outside of Korea. Many popular K-dramas deal with a romance between a man and a woman who is younger than him. Thus, it is likely for her to utter the word, 오빠.
Other simple Korean words are also used among fans of Korean celebrities.
형 (兄 in Chinese and Japanese)
- hyung (English)
- ฮยอง (Thai)
언니
- unnie / unni (English)
- オンニ (Japanese)
- ออนนี (Thai)
- 欧尼 (Chinese)
누나
- noona (English)
- ヌナ (Japanese)
- นูนา (Thai)
- 努纳 (Chinese)