please help my friend is acting weird.?

I know that my friend values our friendship but when her other friend is around its like she doesn't know me or something. She always hangs out with her "better" friend but she never asks me to hang out with her. I'm ignoring her right now to see if she'll come to me for once. I'm always there for her but I don't think she's always there for me, sometimes I get the feeling that I'm her "backup" when no one else is there. I just want her other friend to break her heart in some way so she'll come to me for once! I need some advice on how to tell her how I feel because I'm not good at "letting people in" and it puts me in a very vulnerable position. What should I say to her?