This girl is making a fool out of you sadly. You should cut contact and move on. She wants it all, she's keeping you in her life and stringing you along so that if things go wrong with this other guy she can have you back.
Do you really want to be second best? Do you really think you deserve this kind of treatment? No you don't! You deserve better, you deserve a woman that will have you as her number one and doesn't drop you when someone better comes along.
End it now and don't let her get in your head. Don't believe what she tells you, she is using you and keeping you from possibly meeting a nicer, less selfish girl. Take control, ignore her and don't be her fool!