Should I write her

I'm thinking about telling this girl I had a crush on her since the 10th grade ( I'm 21 and she's about 20-21). But here's a couple problems I don't know if she's gay (I've heard she had crush on her best friend in 11th grade..this information came from the best friend...who's a girl) she has joined the navy, and she's currently stationed in Japan ( I think on aircraft carrier) so the only way, I can tell her that I like her is threw Instagram, Facebook, or somehow get her Phone number, or write her a letter. However I'm afraid to tell her. Not that I'm afraid of rejection, it's just every time I told a girl that I like them, they would tell everyone that I did, or they would throw it back in my face and laugh at me, or show everyone what I wrote them. What should I do? What should I say? Should I even tell her at all? Or should I let it go? Any ideas or tips are welcomed

Why not contact her as friend just seeing what's she's up to these days. And No I would not tell her about your crush. Usually in a normal conversation you can usually find out what's going on with them. Keep it casual and friednly. I would contact her through social media rather than a letter.