Will I get chicken pox if my sister has it? And how do I prepare for chicken pox if I will get it?

Almost certainly; it's a very infectious, highly contagious disease. If you haven't had it before, and you are living in the same house, there is a very high chance you will get it. It's spread in the same was as the cold and flu virus. There's nothing you can do to prepare, really. It tends to be less severe in very young people however, we would normally recommend antiviral drugs for adults and teenagers who present with a chicken pox rash....to reduce the risk of complications which are more common in older people. If you get a break out (there is an incubation period, so you won't notice anything immediately) speak to your doctor.

Get some chamomile lotion for your sister. It is said to help. Meanwhile if you get it, congratulations. You will have lifetime immunity. Drink plenty of fluids, rest, and use that lotion. Oatmeal is supposed to help also. Good luck and hope you feel better soon.