My mare does this. With her case, its because she gets stuck in certain places in her neck that makes the correct shape of a bend difficult.
In your case, it could be an evasion, but most likely she's doing that to avoid something going on in her neck.
Did you mean that when she tilts her head her ears go left, or her nose?
If her ears drop to the left, then you need to gently hold the left rein, and when you use your right rein you will lift it straight upwards and sort of make an "earthquake" in the reins to make that place she wants to go not so inviting.
If she tilts her head to where her nose goes left, and ears to the right, same thing but opposite sides. Hold the right, up with the left. When she tries to fix herself dont throw the reins at her and release everything, just quietly let her be and push her with your leg to ride her towards the bridle.
Before you get on you can hold the bridge of her nose and rock her head back and forth to see if you can get her to give in the area where her neck joins the cheek bone.
The area in red is where you need to see the flexion. It is not a flexion that the horse's neck gets more curved, the flexion will go right or left. So as you ask for right bend, that area will be flexed along with the rest of the neck. Make sense? The horse can bend its neck in other places without truly bending in that particular spot, which is where you get the annoying head tilt. :)
You can stand at her head, on the left, and take the left rein and bend her head left. If the area in red doesn't look like it "bulges" out and away from you, she is not bending there. Tough thing to fix over the computer, but can be helped by just being aware of what's causing it. :)