When I asked her out 8months ago.. she rejected me because she had a breakup at that time because her ex-bf cheated on her twice.. After 5 months when I moved to another country.. she said she now undferstands how much I love her and asked me out.. now Im dating her for 4 months and she still says I can get a better girl and asks me "Why do I love her?" I asked her not to say these things to me but she wouldn't listen.. Im afraid.. Is she trying to get rid of me? What should I ask her?

No she isn't trying to get rid of you at all man. Instead she still feels worthless because of the previous cheater. I suggest being supportive and just keep telling her that you aren't going anywhere. She hopes that you won't leave, or she would have left already. Just keep convincing her that you are better than her ex and that you are not going to find anyone else. Mostly show her that you mean business, show her how serious you are about her. It'll take time but you will eventually get it through to her. Could take months fyi

Support her because she seems really insecure

now Im dating her for 4 months and she still says I can get a better girl and asks me "Why do I love her?" I asked her not to say these things to me but she wouldnt listen..Im afraid..Is she trying to get rid of me? What should I ask her?

In fact, she knows that her feeling for you is getting deeper, and like to find out if you are really serious about her. She does not want to get hurt. She likes you a lot. Give her all attention and love you have, and firmly confirm your love to her ALL THE TIME.
You guys are in honeymoon period indeed. :)

She's just full of insecurity. Just be there for her and show her you care and everything will work out fine.

She's feeling extremely insecure. You're going to need a lot of patience with her to make this relationship work.

It's going to take time for her to build her confidence and self-esteem.

If you want to make this relationship work, then I suggest that you keep a cool head when you talk to her. Provoking an argument is only going to make things worse. Be patient and keep things positive in your conversations.