what should or shouldn't I tell her?

I have a girl that I like a lot, but we can't be together for some reasons. She will be leaving the country soon. Should I tell her the reason why I keep a distance from her or should I pretend we never clicked? She is very kind and sweet, so I don't want her get hurt. I just don't know how to handle all my feelings, and I don't know if she is waiting for my answer. Please help me....

If you can't be with her, don't confuse her by saying anything. Keep it to yourself.

Than you. Even though I don't want to lose her as my friend, but this should be the best to both of us.