Thinking of an escape

Cant sleep. My roommate talking to his gf. And his gf is my god sister but he doesnt know it. Now that my god sister is his gf, but she didnt tell mi. I know abt this matter from him and i am so angry cos my god sister keep saying that there is nothing between them. Keep saying that she has her principles that she will not be with a guy who already has a gf. In the end, i found out that she is with him liao. Damn pissed. But what can i do? Cant do anything abt it since she want to be dishonest abt it. She keep telling mi that she will be there for mi and will always help mi. But actually, she is just humoring mi. Just trying to make mi feel better. But to no effect, now that i have found out abt this matter. I have been asking her all along but she just refused to admit to it. Dont know how should i face her now, after knowing that she has lied to mi. Been doing a lot of thinking, should i go back to singapore and not come back to the US. At least in Singapore, i have my own circle of friends to back mi up and at least i have my family with mi. Down here, i feel so lonely, so left out. Can anyone tell mi what to do? Give mi some advice.