I am seeing a girl that I like, There is potential for this to be long term, I have been friends with another-?

-girl for years before this potential entered my life, this girl likes me a lot and continues to tell me even after I have made it clear there is nothing more than a platonic friendship, she continues to say I have made a mistake and I should give us a chance, we are great friends but this is making me uncomfortable, What do I do?