Uneven walls

A few days ago I was excited to put some border in Rachel and Mayah's room. It is very cute and so girly just like Rachel loves. It has pricesses all over it. I was amazed at how easy it was to put up. Rachel wants me to paint it pink but now then you will really be able to tell that it is uneven if I paint.

There were times I had to take it down and put it back up but it sort of pulled off some of the paint. When I was done I looked it over and realized that one side is off by quite a bit. I just KNOW that when the builder put those walls up he must have measured wrong. I know this because I measured and measured to get it just right and it STILL didn't turn out even. I tried explaining it to Don but he doesn't think it has anything to do with the builder. I wonder what he thinks it has to do with then? Can anyone tell me? :)