When you two are alone put yourself in a position where she can see that she excites you - an erection is good- even a little precum stain on the front of your pants. If she keeps staring you can take it to the next step if not - go to the bathroom and relieve yourself but let her know that too.
sounding like a loser here, there are plenty of non related females go find one of them
Ask her out on a date and work from there.
Get Her Drunk And Flirt With Her And Dig In Her Pants And Finger Her ***** And Take It Slow
Baredevil has the right approach. If she sits by you, put her hand on your stiffy.
put your favourite glows on,take some lubricant and keep on dreaming.Bay the way:can you introduce me to your sister ?
Do you really think that because you want to do something it is going to happen. In the real world that isn't the way it works. You might date 10 women and maybe have sex with a few of them. Your odds are so off when you consider the fact that she might slap you into the next century. I would say if you don't want to scare her half to death just let it go and have a fantacy about that all you want just don't ever make the effort to actually do anyting. It will get back through the family and then you won't be trusted with any female or male in your family.
become an even bigger d*ld*
You need help. Find yourself a good psychiatrist who will help you with this problem.