What works best is to avoid the tension for both of you in telling her you like her. Just show her you like her by giving her a lot of attention and offering to help her any way you can. Comments like, "Wow, you look good in that outfit" or even bolder, "I think you and I would make a great couple, what do you think?" said with a big smile on your face. That way, if she rejects the idea, you can come back with, "I was joking, I'd never date you." :-)