My sister is gay

My sister is gay...apparently. (She brought home 'Leah' last week) I was a little repulsed and spent the entire meeting hiding in the laundry room to escape the awkward silence coming from our living room..... It just doesn't seem right.
And get mad if you want, but it seems a little gross to me. Man and woman...it's pretty darn simple...and yet, we managed to get it screwed up. I'm just not comfortable with the idea... And yet, I'm convinced that that doesn't make me a terrible person...