If she says she doesn’t see you that way, she may just not see you that way. Girls are weird, man. They say one thing and act another way. Maybe they’re too stubborn to say that they want what they actually want, but none-the-less, that is just what girls do.
Just talk to her, tell her that you know she said she doesn’t see you that way, and ask her if she doesn’t actually see you that way or if she doesn’t WANT to see you that way, huge difference. Tell her that her actions don’t fit what she says, and that if she isn’t into you she needs to stop treating you like she is, because it is giving you the wrong idea.
If she continues on, give it a week then start ‘crushing’ on one of her least favorite girls that she knows that you can actually tolerate, it’ll drive her nuts and if they aren’t on speaking terms, there is no way that other girl can find out that you pretended to have a crush on her to annoy your best friend. And if she is jealous, you can throw the “Well you said you didn’t see me that way…” argument back in her face.
Extremely childish, but definitely will be funny and/or fun and will get your point across.