I just refuse one girl !!

Well I applaud you for being that honest upfront. I think for others that girl may have been taking advantage of other men knowing that girl is openly saying that she likes somebody. But in your case you said how you feel and you were honest and just being frank about your situation. If you are concerned about her feelings maybe the least that you can do is befriend that girl and try to guide her feelings away from what she is feeling right now and maybe someday she'll find someone that will love her back.

[i]That's okay to refuse the girl. The most important thing is that you refused her in a nice way. You are different from other guy. Most guy would take advantage of her love. Used her and discard her if they find another girl worth their time. Eventually she will find the right guy for her in the long run.[/i]

I think you should be honest with what you feel for her then she expect that you will like her later. Girls are very emotional! Then in a long run she will hate you for it or make an excuse that yes you like her but you like her as a sister nothing less and nothing more than that. Talk to her in a suttle way that she will not cry that you will still be there for her a real friend a brother.Have a nice day!