What do I do please help me? I could really use as many answers as you can give this is very important?

I met this 24 year old italian girl in Italy over the summer. Im 18 and American. We went out and made out that night. That was it. She writes letters to me now alot. I wrote her because she said we have to keep talking once i leave. In her last letter she wrote "it might be too soon and i might sound immature but i am in love with"...."when i am with you i am a different person usually im a little shy and with you im open"....i worry that youll forget about me and find another girl"...."you can be sure of this no guy will ever distract me from you and you are the only one i want to be with"....when i look at your picture i cry because i cannot be with you right now". When I first read the letter i was like awww but then the second time i read it i was like what? my stomach turned. now im scared of being with her why? i really like her but im scared now for some reason. like im having second thoughts about her now.i mean we really only went out that one night and made out thats it.