Horses are all naturally a bit one-sided.
Some things to check before anything else - saddle fit and chiro issues. If she's stiff one way, or if the saddle is impeding her movement one way, that can manifest in that off-balance look.
For your position, I recommend just working through the unbalance. Allow her to take all the room she needs to feel comfortable moving on the circle and don't force a smaller circle before she has the strength and balance to manage it with a little effort. I would also lunge two circles the stiff way for every one the "good" way, as a general guideline.
Long reining or side reins may help, but I definitely recommend using those only with the help of someone familiar with their correct application as they can do more harm than good if they aren't used correctly.
In general, make sure that you do everything on both sides, on the ground and under saddle - that will do a lot to keep her from getting too one-sided.