Just a phase?

My oldest Olivia is 6 years old.. and lastely she cries about everything. She cries if she doesn't get her own way, has to go to bed, even something as simple as she can't go to the bathroom right away because someone is in there. I am not sure if this is just a phase or what? I don't mind her crying but it has gotten ridiculous.. and then she cries more because her sister tells her she is a cry baby! Her 4 year old sister I might add.
I am hoping that she eventually grows out of this since first grade is right around the corner.
Also, my kids have been fighting like crazy lately. And if there is ever a lull in the fighting one of them just HAS to nitpick on another to get things all stirred up. I think that is what makes me even more crazy..