Ok I'm a guy... my girlfriend still likes me we just said I love you to each other... One day she asked me if she could date her ex... Even though we are still dating.. She said its up to me if she can date her and our parent would never know about her ex and her... I said no to the dating her ex... But I asked my girlfriend if she really liked her ex... And she said she did... And now about a week passed by and she says she's chilling with her ex lately and I don't know if she is dating I'm all good with her messing around with girls but not having sex with girls... I was with her today and we were all good till I left and I texted her about 30 minutes after leaving and she was with her ex... My girlfriend said she wouldn't but I'm not to sure anymore so are they dating with out anyone knowing or doing it...

Talk to both of them together! You want to know what the deal is, ask both of them. Your girldfriend... although she sounds very open about what she wants and what she is up to... in a way she is also leading you on. You said, that you don't want her to have an intimate relationship with her ex. People usually don't hang out with their ex when they are in a new realtinship.

You girl friend obviously does not want to date you exclusively and that is what you want.
Why are you staying with her knowing she is doing what she wants regardless of what you want?
If she wants to date her ex, let her, but she needs to do it without dating you too, and she is already doing that.
Leave her.

I wouldn't really trust her that much myself, but since she denies any hanky panky, how would you prove it? Bi, gay, straight, makes no difference to me, you don't hang out with someone you admit you want to knock boots with, and tell me ain't nothing happening.

I think you are just her cover, and the girl is her real lover. Just My Opinion though. Don't make her lie to your face, dump her if you don't completely trust her, or can't deal with her closet BI-ness.

If this was a man, not a girl and she was "hanging" with him, what you do or think.
I agree, you said she could not date her, so now they are hanging out together, same difference.

Cheating is cheating, if bi, gay or straight, so she wants to date you and girl friend and not be true to either. Your choice,