My lesbians gf is going to marry a man!!

Hi what should I say? My girlfriend is a closet lesbian who will be marrying a man on Feb 2015 for her family and her social environment. I have been together with my gf about 2 years. Since the beginning of the relationship I had known that she has pretended boyfriend and I don't really care about it. She and her bf are together about 2 years too. She started dating him one month before she met me on lesbian website. She always said to me that she needs him to pretend that she is straight to her parent who are very homophobic and kept saying gay people are disgusting. We are Asian oriented ( Thai) so she has been taught to follow her parent's wishes. She is also scared to admit to everyone that she is lesbian. She said that she is terrified to come out to her friends and family. She doesn't have any best friend but a regular friends who she try to stay connect and hang out occasionally and her social circle is only interest in her beneficial gain. The man she is marrying is the son of an influential man in Thai coup party. So now everybody is surrounding her so they would be able to expand their connection in Thai political group and other high profile people such as son of diplomat or head of ministry of foreign affairs. She said that I am the only one she trusts and love. She is doing the marriage for her family reputation. She can never like man. I am trying to understand her and accept this problem but it hurts so much. I am jealous of how perfect he is and how he gains my girlfriend family support because they r acceptable straight couple while I have to hide and pretend to be her best friend in front of her family. I also own a few businesses and I think I'm better than him. It's just that I am a woman and not a man. She knew that I am deeply in pain cos I vent my stress and frustration at her. We fought a lot. I want to stop and walk away but I love her so much. I do want to have future with her. I don't know how long I can go on. I know she is doing her best for our relationship too. She endures my mood swing and doing everything she can to please me. She said she is not scared to get divorced. Next year she will be moving in with him and our relationship won't be the same. She is confused and I am also confused. I don't know what to do. She has me as her only best friend and I also have her as my only best friend too. Should I wait and see until she can't handle being married with a man? Sorry for my bad english. She did tried to declined the marriage proposal by telling her parent and her bf.
She said she doesn't want to get married to her parent but like how Asian parent do is both my gf's parent and bf's parent arrange it without my gf's consent. I don't know what to do and very confused.

 

Thank you for all your advices. We had a lot of serious conversation but it didn't help to ease the tension or help to resolve our problem. We have come to a point of breaking up but we couldn't entirely cut out our communication. We think that we will try solve this problem step by step. The real problem is her mother. Last night I stayed overnight at her house and this morning I ask her to drive me to work. Every morning she always drive her brother to work but it's just this morning she has to send me. Her mother called her and said can u stop being a lesbian? Ur friend come and stay every week and have sex everyday. I can't accept u being a lesbian. I hate lesbian. It's disorder. Does ur boyfriend know that ur friend stay with you almost every night? When can u stop playing lesbian? I will bark into ur room one day to see u guy have sex. It's disgusting. It seem me and my gf are in the losing battle. Her mother won't accept us even she knows that her daughter is a lesbian and she is doing the marrige on purpose. My gf has never been out of her parent sight. It's so hard to see me and her in this unfair situation. Can u really leave her if u know that she is also in so much pain too? I am her only best friend as well. We decide to keep our distant. I wish my gf has more courage to face her problem and I wish she fight for us more. However I do understand her that if she chooses me she would lose her family which she cherish the most. Her family is her life and lesbian is who she is too. I don't know what to do and hope that God and time will help. Thank you. I am also not sure of what to do. My head feels so numb.