And try multiple figures in those certain areas
Let her loose in the ring and try handwalking her around a few times and reward her when she doesn't spook.
Maybe if you walk your horse in hand around the arena going right into the corners, and standing there for a minute, she will get used to them. Do this maybe before you ride every time and she will get used to it. :)
Maybe try circling multiple times at any speed to get her used to that area
you could try walking her round in hand then have someone walk beside you while you are riding then eventually she should be more confident
Just keep riding till you finally get her/him in the corners