I would care for her out of obligation, I'd try to make her life as comfortable as possible, probably dedicate a youtube to her or something, find a way to engage her, as sick as it sounds, that would be somewhat of a project for me that I'd enjoy.
But, if she was completely unable to fulfill my physical needs and assuming she knew that, we'd have to figure out a way for us to get around that. I would be in true agony if she still required me to be "faithful" to her physically. Assuming of course she was still mostly functional... If she was straight vegetable, like, pull the plug let her go man.
I mean, it'd have to be a really awkward scenario... like, she'd have to be unable to feel for it to really ruin it for me... 99% of my pleasure when it comes to physical is hers. If she gets where she wants to go, I feel like a bad ass, like a true man, I don't really care much about my side, that's easy lol.
I mean, I think a better "doom" scenario is she develops a thyroid issue which makes her gain weight incredibly easily, and she just can't really avoid being over weight. In that case, yeah, I love her out of obligation, but I'd definitely hate it, I'd consider that side of my life over, probably try to chemically castrate myself or something. What's the point of having a sexual desire with no way to fulfill it but hurt someone you care about?