I share a room with my neice who is five. We want our bedroom done, trouble is we both want different things and we get nowhere because she changes her mind constantly or is stubborn about her one idea and i am apparently just as bad. how...?
You could each choose a paint colour for your half the room. Put tape down the middle of the room dividing it as equally as possible, then painting each of your halves the colour you chose. Then once it dries you can decorate your side with posters, news articles, etc. While she decorates her side with stickers, glow in the dark stick ons, etc. It's amazing the endless possibilities.
She's indecisive so, set down some rules. Actually don't paint her side of the wall leave it as is. Wait until she's a tad bit older to decide what side to paint her side of the room. For now just give her things she can stick on the wall, that'll keep her entertained. (i.e things that glow, light up, flash, glittery, etc)
Well on your side put what you want and on her side she can have what she wants, problem solved :-)