Other Answers (3) your not gonna like it but you will just have to share and compromise, you will get used to it and so will she and then you will get used to be around eachother. lots of siblings share rooms so im sure you will be fine :) i have the same problem with my brother!! he is just being nosy but always breaks my things!! the best thing i could recommend (even though it sounds weird) is hiding things at the bottom of your underwear drawer 'cause at the end of the day why would she look there? and keep them in plastic bags as well just in case. another place to hide things is inside your pillow case or under your matrice or under your bed if it is low. a way to decorate could be by splitting the room in half (metaphorically) using the door as the meet point with your stuff on the left and hers on the right or vice versa! you could try getting her the same make up as you as a gift so she wouldnt have an excuse to use yours!!