I know something about having an ill spouse, and I agree completely with Kurious25 that she might be having trouble letting go at all, she is probably so vigilant with you. Before you move back to bondage, I would see if she can even get into, say, the momentary release of a hard kiss with her hair pulled back, or whatever have been quick and temporary submissive triggers for her. How is she during sex? I'll bet she's terrified. I think you need to go slow, slow, slow, and keep talking about how you both feel. I hope you don't try to talk her out of her feelings - I'm scared I'll lose you/no don't be silly I'm fine now. She IS scared she'll lose you, no matter how you feel about it, and you need to give her slow and easy ways back into the submission.

In terms of the bondage, yes, I think mental bondage and then symbolic bondage like a body harness, and then something that she can get out of easily.