I know that some may say that you married her "for better or worse" and that you have an obligation to her--and they have a point. Others, like the above posters, say you have a right to a life. I think the correct approach is to be frank with her and to explain that, while you love her, the only thing that would permit you to live as a man again would be for her to receive the aid she needs from others, as it is too depressing to you, disconcerting, and uses just too much of your time.
It is one thing when someone files a no-fault divorce because they have met another person and therefore wants to "ditch" a perfectly healthy mate. It is another thing when they want out of a marriage to avoid a lifetime of slavery to someone as a provider of support, nursing and care--in return for basically nothing. The solution may lay in the grounds provided for divorce by state law for situations like yours, which may be much kinder to you than normal "no-fault" grounds are in regard to alimony. In any case, your alimony should be no greater than that which would have been "minimal" if she were not disabled which, if she worked before her disability developed, may be virtually zero. If this turns out to be true, then Social Security should take care of her care thru early medicare if she has any significant assets after the divorce, and SSI should do it if she does not have assets. You have to find a very good lawyer, who is familiar both with family law and Social Security regs.