ok heres the story....

i went into old navy once with a buddy was his wing man he was trying but didnt succed on getting a girl, the girl he wanted had a friend whom i really just wasnt paying attention cause idk just didnt lol....and so anything i talked to her a lil bit but didnt think anything of her...so then months go by and i start talking to this chick on myspace long and behold its the chick i was talking to at old navy (she works there) so we met and instantly we hooked up...no problem ive slept with her shit tons of times...now one day i noticed on her page a girl whom is her best friend who is hella hot and i want her....though now me and that girl had a down fall cause i made her bealive i liked her blah blah just so she would sleep with me you know, and i have kid around about me hooking up with her friend but she gets mad...so i said id stop...no again me and this girl are no longer hooking up cause she cant keep her legs closed to 1 guy sooo....shes talking to someone else, were on good terms we talk as friends but i added her friend on myspace and kinda sorta talked to her just stupid shit but my question is how could i get her best friend? what is some good advice as im sure the girl told her friend you know dont date him or something idk....so what would you recomend how to start talking to her and ease my way in or what????