Here's what you should do:
Tell her that you're interested in her. If she says, "I'm not interested in you that way -- I think of you as a friend". Reply, "Ok, having you as a friend is good enough for me". Then be the best friend possible. Since you are happy just being around her, you will start exercisng. If she ask, "Have you been working out?" Reply, "Why, yes I have -- thanks for noticing!". Then continue to be happy while she is just your friend and you see her going out with other guys. Since you are happy, you will become more successful in life. You might get promoted and earn lots of money, buy a nice house, a nice car and stuff.
After a couple of years, she might start to "notice" you. You've been working out, you have a great job, make lots of money and is a great and loyal friend to her.
Now, if she makes a move and tries to kiss you with the hope of moving beyond the friendship stage, pull back and say, "What are you doing?". And if she says, "I think I have feelings for you". Reply back with, "I only think of you as a friend and I don't want to ruin this great friendship. I'm not interested in you in that way".