Just say it and what happen will happen. Be serious about it so they don't take it as a joke.
Also, Girls (by Girl in Red) is a great song for sapphic pride, and I always feel really nice when I listen to it (mostly for lesbians/bi females, but boys can listen too!)
If you are still having trouble, maybe repost this on the LGBTQIA Club, there are more people that can help you there!
Best Wishes