I'm in love with one of my good friends

Whenever I see her come online in Skype, my stomach does backflips. Her personality is absolutely amazing and complementary to mine, and we share many interests, drawing and the same movies, to name a couple. Every day, I tell myself, "This is it. You're going to tell her how you feel."
But I never do, for 4 reasons. She's 9 years older than me, lives on the other side of the world, wants to stay single, and I'm 99.9% sure she's straight. For weeks I've hoped it will go away like any simple crush, but it's always stayed. And even with the reasons I stay silent, I still long to tell her.