She broke up with her boyfriend. do you think she will come back to me?

ok so this girl i like i've been talking to broke up with her boyfriend for a while but months later got back together with him. when they broke up i hang out with this girl a lot and things were going really well and i thought she really liked me. so i decided to ask her out but then to my suprise she said she only sees us as friends. that really suprised me cuz the signs that she liked me were so obvious that people started asking if we were dating. i still hang out with her now even though she is dating her boyfriend and i still think she likes me. she calls me her best friend and she doesnt want me and her boyfriend to meet cuz she says it would be awkward. anyways i still think this girl will eventually want to date me when she breaks up with her boyfriend for good but i kinda feel like shes using me as a backup or second choice. so if she decides to go out with me should i go out with her or just say sorry i dont wanna be your second choice?