I hate to say it, but women's sizing can be even more confusing than men's sizing. Depending on your body, you might find you can fit into both misses and juniors clothing in certain sizes because they seem to overlap. Also, I find that I need to buy one size smaller if the jeans are stretch and therefore supposed to fit closely. Depending on how and from what the bottoms are made, I can fit into sizes 5, 6, and 7. For tops it's usually medium in misses, or large in juniors.
I even wear different sizes in shoes depending on how they are made when it comes to tennis shoes, heels, or boots. Trying things on is really the only way to figure things out, otherwise it's a whole lot of trial and error and returns.
~April