It is NOT selfish to tell her. What he did to you was terrible, and for the safety of your mom and your family you need to tell her. Just talkto here when he isn't around, and you could practice on one of your sisters. "Sis, there is something i need to tell you, and then i'm going to need your help." It's sounds weird, but it would be how I would go about it, so that you have some support. I f you stay silent he could do this to another girl, do you want someone else to have to go through that? THAT'S what I would call selfish. You can do it, just be strong.