When you say you can only get her so far and then she'll just stop dead and try to spin around back toward home, how long do you spend trying to keep her there? Every spring I have to spend my first few rides convincing my horse to go past his comfort zone before he remembers he likes to go out on trails and stops putting up a fuss. Two years ago, there was a wood pile that he would not go past no matter what. He'd try to spin around over and over again rather than go past the pile. Someone suggested that I had to be more stubborn than him, so I tried it. I rode him toward the wood pile, he tried to run away. A few dozen one rein stops later he switched to planting his feet and we proceeded to stand there for a good 30 minutes. I would not let him graze and made him stand there until he finally gave up, let out a huge sigh, and walked calmly past the wood pile. It's never been an issue since.
Long story short, take her out there to her turn back spot, ride her like you expect her to keep going or else you'll have already lost the battle. If she does try to turn back, don't let her make a complete turn. Turn her back the way she tried to turn. If you allow her to make a circle, she'll think she succeeded in turning away. Assuming you can keep her calm, just sit there until you outlast her. Stay calm, breathe and make sure you have all day. Even if she just moves forward for a few extra strides, reward her effort and turn back when YOU want to. I'm sure you get the idea. The name of the game is, be thicker than your horse.
You just have to see your distance...you don't have to like it.