WOW!! Ok you ar ein a dharma sankat- what do you want to do? You see beta, the issue is that this is really playing with fire. What if someone gets to know? What if she really has feelings for you, gets possessive, gets pregnant with your baby?? How will you handle all this what if she begins to make demands? And Beta, people are not so stupid, you come and go to her new marital home, wont people begin to talk- have you thought about that?And finally, she is a sister after all!!Think before you take any step which you will not be able to retract!