"GNN" is not a commonly used acronym in everyday conversation, especially in a romantic or friendly context. It's possible the girl is using a unique code or abbreviation specific to her group of friends.
To understand what "GNN" means, you can ask her directly. For example, you could say:
- "Hey, I saw you text 'GNN', what does that mean?"
- "What does 'GNN' stand for? I'm a little confused."
If she doesn't want to share, respect her privacy and move on.
Remember, clear communication is key in any relationship. Don't be afraid to ask questions to ensure you understand each other.