Help me solve problem with my adopted girlfriend

Hi! First of all I am not an adopted, my girlfriend is. She is 26 and I am 28. Her origins are interracial and she is adopted in an international family what is unusual in the European country we live in. I have many problems with her. I am not sure if it's because she is adopted or we are simply not thinking on the same level. That's why I am looking for help here. She told me she was adopted first day we ended up together, as some other personal things. She got adopted when she was 3 years old. Growing up with her neurotic father that used to beat her. I tried to talk with her about it, but she is refusing, saying that she is normal and doesn't like people looking at her that way. like it's not important, it didn't influence her life that much. ( she has talked with her bio mother for few hours) To get to the point, our relationship. From the very beginning she was very interested into my sexual past(I was pretty active and have cheated before what I have told her, grrr), she was playing detective to the details. Now she doesn't believe me a thing even though I haven't done nothing to her. I had to convince her that she is better than anyone I had before her, and that she is the best in the world for me in any aspect. The problem are the females that pass us by on the street, my ex classmates, my female friends, women on TV...everything. She was pretty active in the past to and had lesbian experience. she has lots of lesbian and gay friends and all kind of "weird" people around her. Also she is keeping in touch with her ex partners, not the ones she had somewhat serious relationship but the short term sex partners. she said they grew up to good friends. For the guy from the longest relationship she was talking only bad words at the beginning but later on started talking like it was lots of her fault. Many inconsistency. In my mind, if every girl is a problem for her there must be something going on with some of these guys, that's how I was thinking and slowly became jealous as she is(I have been cheated on in previous relationship and was hurt a lot). The difference is when she gets insecure I am trying to talk and explain there is no place for worries, in her case it's "you gotta go to doctor", psychologist and such things. But in no way she needs help. As we were just starting our relationship she was the one that said that just wants occasional sex, then later she wants us to be a couple, then changing her mind and when I would say ok you're free to go, then she would change her mind again(though she does it with many things). I had to listen things, your mom is a whore, your friends suck, all my ex were better than you, I will be unfaithful to you, you didn't finish your studies(she doesn't study at all) and such things to get me mad, insecure and so on. Or trying to make allies of my friends and make fun of me. Calling my mother talking some things about me that should have stayed between us, and when my mom said, and what about you, she would say, well I am just a bit complicated. She thought to make an alliance with her to, which normally didn't work out. Whenever we have a fight, she runs to her friends, her ex or mother and talks about me in a bad way. I know I do some bad things sometimes, but nothing is one sided. And in most of the things there are double standards involved from her side, with poor arguments. From what I have concluded might be possible is that she needs drama. She is very stubborn person. She has compulsive disorder. Seeks for problems only in me, whatever I say to her it's like she doesn't even hear me, she is lying(hiding) to me sometimes etc etc I could go on for hours. Someone could ask me, just like my friends, why are you still with her?! Whenever I would try to split up, she would "grab" me and have her explanations of loving me so much, I don't understand this and that, I need help and so on. Once she waited for me 6 hours in front of my door(that was before we started living together). She is sometimes so loving and tender, positive, full of imagination but in other cases she is my worst foe. I need help here, which is obvious. Is this something her adoption has to do with? How to deal with it, or any other advice... I am thankful in advance for any of your advice to help me find a good way to solve my situation! Greetings! S.