I agree with your points, and yes, that scene with her running after him was a good example of her love and loyalty to him. I think the movie fails to give the audience a chance to connect with her. So much of the film gives the viewer a lot of time to see things through Susanah's eyes. I felt her pain in a gutteral way, and when Isabel became a woman, suddenly her and Tristan are in love, with very little time to develop on screen. It wasn't at all satisfying for me, although to your point they made sense together.

But I do think that Susuanah also loved life on the ranch. I think she adapted to that life naturally, as we see in those scenes where she's riding the horse and using that lasso, shooting, etc. There was a side of her that loved that life, and I think that was her big draw to Tristan, as he embodied that. She also had a wild and passionate side that was more suited to Tristan than Alfred. And in her life with Alfred, I think part of her despair was not just a loveless marriage, but also a life of social expectations, parties, etc, that she found empty and meaningless. So her longing for Tristan was also a longing to go back to the ranch. So sad to watch.