approach and retreat.
Work on the ground first because it's safer.
Walk her slowly up to the woods. The second she becomes uneasy, turn her around and walk away. Horses, by nature, are prey animals. If they are frightened by something their natural reaction is to run away or else get eaten. You've got to prove to her that the evil dark looming woods is not going to harm her in anyway and infact it's a good thing. Forcing her to go over there will only make matters worse, it will make her react and her trust on you will diminish because you, in her eyes, are taking her to her death.
So as before...walk her up until she starts getting uneasy. The second she does, turn her around and walk away (but don't let her run...if she feels the need to run, you took her too far...past her breaking point). Once you walk her away, give her a pet, and then head back. And repeat.
Remember to ALWAYS turn her around when she feels uncomfident or else you or her can get injured.
Soon she'll go farther and farther until she can walk passed the woods with ease. Some horses are naturally afraid of things where other horses were born brave...it's all about approach and retreat.
You would also do the same thing in the saddle if she has difficulties with that.
I know this does work because I've used it with my horse and at least 6 other horses before. My horse hated tarps...he'd bolt if I brought him towards one and he wouldn't walk on it. With a few (really only 3) approach and retreat excereizes he'll walk on the tarp, trot over the tarp, and even canter over it. I did not force him to walk over it, I took it at his own space and because of that he realized that it wasn't going to hurt him and that he can trust me because I'm not going to force him to do something that he feels is dangerous.