I've had attraction to a first and second cousin of mine before. I didn't act on anything and it passed after a year or two. I also had a cousin who had a crush on me. That also passed in time. IN other words, this may not be a permanent thing.
You need to consider what you mean when you say she's "the perfect girl". How well do you really know her? Are you sure it isn't jstu infatuation driving you? Other issues: consider them.
I suggest reporting your thoughts/feelings about her here so that we can help you by being a bit more rational (perhaps).
Finally, if it looks dead determined that you sincerely like/have a crush on/whatever her, then it's ok to tell her casually and say "I really am attracted to you. I know that's odd in society, but I wanted to say that." Say no more, and don't push it. If it turns out she ends up feeling the same, it's possible she'll bring that up with you. If she doesn't, it's not something that the two of you would likely be comfortable with in the future.
>>7 http://www.youtube.com/watch?v=RMqR8-rn_yQ&watch_response