With horses that are afraid of one particular area, I concentrate on working in that area...not focusing on getting them UP to that area, I just work in that area.
If you are afraid she will buck or bolt, and get you off of her, do this on the ground first, so you can get her used to that corner on the ground, and then transfer that to the saddle a little easier afterward.
Lunge her near the area she doesn't like, concentrating on direction changes, and gradually moving closer and closer to that 'scarey' corner, while focusing on maintaining her attention. When you get a certain distance away, just calmly walk away from it for a few moments. Give her a few minutes to rest, then start all over again, ending closer to the scarey stuff before walking away. Your goal is to eventually end with her being comfortable working right in that corner, calmly, and focusing on you without issue...and you taking her away for a moments rest as a reward.
When she is comfortable working near that corner on the ground, start doing the same under saddle, starting a certain distance away, doing circles, serpentines, loops, rollbacks, etc...keeping her focus on you at all times is the main goal, while gradually getting closer to the dreaded corner. The more you can move her feet, the more she will focus, and figure things out. It may sound odd, but with horses, if they are scared, they will run (or fight)...so move her feet...
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."