Your sister is the best friend since birth. She has been there since day one, and will be the one friend who will stick by your side for the rest of your life. The thing about sisters is they are there, even when you don't want them to be. As much as you love your sister and she is basically your other half, you can also fight a lot. In fact, there are some things sisters fight about that we fought about when we were 12, and we still find ourselves fighting about at 25.
You can't help it. You will find little things that you disagree on, and since you're so close and comfortable with each other, you can be brutally honest about it. Luckily, she is family, so you know perfectly well how to handle any dispute. You've been fighting about the same situations for years, so you're basically pros on how to handle it all when you sense a disagreement brewing. That's what happens when you spend almost all of your time with someone you love. You have probably fought with your sister over these eight things, but you both love each other. You know disputes come and go, but sisters are forever.