Relationship with cousin's sister

I am 30 years old male,unmarried.My cousin sister 19 years old proposed me and i accepted.She told me that she loves me since she was 13 years old and she really loves me.She wants to marry me and she is ready to leave her parents for me.But i dont want to marry her as she is my cousin sister and nobody from our relatives will support this also she is not the perfect girls i am looking for marriage.Just i want to have sex with her thats all.Pls suggest me what to do ?

Well dude. Ask urself.