How can i find a way to get along with my brothers girlfriend?

I dont get along with my brothers girlfriend! My dad has an ex wife and they hate each other! They had my brother and then got a divorce soon after (young marriage). And then he met my mom and had me and im 14 and by brothers 21 we finally got in touch and he came out here with his fiance for a week ( i live in hawaii and he lived in new mexico), they went back home and he decided he want to be out here with us and in hawaii so my dad got him a good paying job and we let him stay with us. A week after he was out here him and his fiance broke up. A week after they broke up he went back to new mexico for thanks giving to see his grandparents and mom and step dad. Before he left he got on facebook and started writting this girl that he dated that was crazy about him in high school. She picked him up from the air port when he went home for thanksgiving. and 2 weeks later he brought her out here to live with us for a few weeks till they found an apartment and they did and they moved out and now i hardly see my brother and his girlfriend is really fake she acts like where bffs infront of my brother and when hes not there shes kinda a *****! Shes very controlling over him! So after they moved outta our house they invited us over to see there new kitten (witch they gave away because the cat was sleeping with my brother and snuggling up to him and she wasn't, she was jealous of the cat so they gave her away.) She hyperventilates when my brothers on his way home from work like when hes almost home and she runs arouns there apartment and rolls in his clothes and hugs them and smells them. My birthdays in January and that was the last time i saw them, i finally saw my brother yesterday and he took my to the beach with his awesome friend ben, then after his gf was done working we left the beach and picked her up and went back. I saw my brother in between the January and March time period i forgot, i saw him for like 2 minutes when he rode home with our dad and then left, and he came over for like 10 minutes to return our dads truck that he was borrowing, he has his own car now. My point is that she doesnt really let him come over and see us, and shes just a *****! Like my mom and him are really close she used to take care of him when it was our dads turn to have him so we all love and miss him. and i just cant stand his girlfriend and i was wondering if anyone had suggestions on how i should deal and be nice to his girlfriend because im pretty sure where stuck with her, there where talking about having kids and when there gonna get married :( like nobody likes his girlfriend! my parents family and friends nobody but we have to be nice to her for my brother. /because he would pick her over me and our family in a heart beat. Im not sure if shes just acting because she was engaged to this loser she had a crush on in the 6th grade that she was in love with and she left him to come be with my brother but the catch is he told her how much his salary is and how much he makes a week (1100 a week) and that hes in hawaii and stuff like that. but im not sure if shes not acting because she keept all the letters he wrote her 4 years ago.... so how can i be nice to her on see why shes being a ***** with out losing my relationship with my brother?