This is going to ruin me but i just can't tell her?

You need to tell her, the longer you leave it the worse it will get and you eventually end up telling her anyway because it will slowly drive you insane, so it's best to catch it as early as you can. If you get this out of the way your feelings will eventually fade, but if you don't tell her they will just get stronger. I once was in a similar situation and when I told her I got a no, but we still remained super close and became even closer as a result, so it's not necessarily the lose situation you think it is if she doesn't feel the same.