Say " no sis, I don't do relatives, half or full" If that doesn't work, tell her to watch the movie ' Cement Garden' she will rethink it!
If your age is correct, and her age is close to yours. then what can she actually expect?<br />
Besides, if she has never approached you in the past maybe there is something wrong with her, that is maybe she doesn't remember that you are her 1/2 brother.
Something is not ticking right up there. You need get far far away. When she walks in the room you need to walk out. You need to go beyond saying NO and show her NO!
o dear thats a tricky one tell her straight think of the family damage
At your age, you should be able to simply tell her.
Say you're not into incestuous relationships! Depending on which country you reside in, you'll most likely find it to be illegal... Or at the very least TABOO!<br />
And as LaSenorita so delicately pointed out (j/k) if by some chance she fell pregnant, you run quite a high risk of fathering a physically and/or mentally deformed child.
Tell her no, that is just gross.
exactly like that.