You need to leave her be for awhile...you'll only push her away. From your post you two never dated right? And you mailed her a letter telling her you love her? I gather you havent dated a lot? I dont say that in a mean way-you were probably frightened. But I wouldve waited until you guys established something-a relationship. But you cant take it back now.
You may have freaked her out Greentree. Honestly-and or she thinks that was really sweet-she could have a lot of different thoughts about it. But she was honest with you and told she didnt want a relationship right now. So back off for right now. I mean say hi and be socialable but dont hound her.
If its that hard for you to deal with you should back off for yourself. This could make you nuts mentally-and its not healthy. When the feelings arent reciprocated in that sense-it becomes harder to deal with everyday. And those feelings you have become negative and or obsessive.
In my opinion I would leave this situation alone for youself. If down the road she comes to you with an interest in dating-great! But let it go for now...love does hurt but you took a chance that many dont...
goodluck...
everything happens for a reason...beginning to wonder why.