wow.. honestly bro, considering she kept loooking @ you and smiled and even went as far as adding u on FB, she did her part. all u needed to do was a direct approach (no beating around the bush by asking her an opinion or anything), shoot even marching right up to her the next day and asking her something cocky like, "so hey, do u FB stalk all guys u like or am i just that awesome." (say it playfully or it wont work) woulda worked.. she basically showed u she was interested.sorry to say, but u may have missed the boat brotha.... i would just walk up to her and just start talking to her as if u know her. as soon as u see her as u walk into the gym , say wow the craziest thing just happened to me on the way here! and make up some crazy/ funny story then move into a normal convo. and no, dont start w/ FB convos if u havent already talked to her, it'll show a lack of confidence and she may even think u are scared or intimidated to talk to her (which is natural, i am always nervous before talking to even average looking women.) good luck bro! just do it, walk right up to her. dont stare from a far an hour into your workout. girls know when they are being eye fucked haha. the worst thing that can happen is she might be a little quiet or awkward but whatever right? read "the game " by neil strauss. changed my life bro, and im far more successful than i used to be w/ women.