Take care of yourself. She will obviously be your main focus, but set aside some time for self-care every day (eating, exercise, and relaxation).

It's easy to neglect your physical or mental health in a situation like this, but you can support her better if you don't burn out.

Beyond that, bring a paper notebook and pen or pencil, and take notes during every medical appointment. Those will prove valuable.

Oh yes, and warm socks for her with non-slip rubber on the bottom. I found those very useful during my months in hospital.

This is a tough time. Best of luck to both of you.