We’ve only seen her set out to purposefully make some magic one time, and she was only playing along so the crazy guy would shut up. We haven’t had confirmation yet of what exactly she did to the hat, if anything, though it appears she did something.
She also did something to Graham when she kissed him, though she wasn’t setting out to consciously do anything magical in that case.
When she first set foot in Storybrooke, a powerline sparked.
When she decided to stay, time began to move.
When she put on the badge, the earth shook.
So even though she’s not aware that she’s making things happen, she’s still making an impact. The majority of what she’s done so far is breaking magic, making cracks in the curse, as opposed to making magic. And August needs her to believe in order to break the curse’s hold on him. The hat is the exception, but like I said, we don’t even know for sure what happened with that yet.