What should i do with this girl? is she playing with my heart?

okay, me and this girl have been talking & we started liking each other.. so we been talking for a while now and we love each other. but we still don't have a structured relationship. so we're still classified as "talking" this isn't some stupid teenage stuff.. like this is real i have so much feelings for her, and i think she felt the same way. until yesterday i decided to man up & ask her.. why aren't we in a relationship yet, and then she said "i don't want a relationship" and i'm like "ohh?, why not" but she couldn't give me any logical reasons.. the thing is... she was in love with a guy for 2 years.. but she said i stole her heart. and i said i was worried that it might happen to me too.. (someone might steal her heart from me) .. then she reminded me.. "you stole my heart from him, remember? " and i was ohh i never thought of that. then she was like "well i think about it everyday" and that made me think.. does she really want to be with me? is she still in love with this guy? soo i made up my mind. and said.. " you should go back and talk to him," then she said " hush, i'd rather not" but now i can't understand whats going on... it might be just me or things have been a lot different. i don't know if i trust her anymore. i think she's talking to some other guy.. and i want to let her go, but i don't at the same time. :/ can someone please explain to me in full detail what i can do? please & i'm sorry if this wasn't explained very detailed. i'm thinking about the situation at the same time..