I would just keep filing Joint. I don't think there is any advantage to filing MFS or Head of Household. And she would also have to file a separate return and all her SSDI will be taxable.
What do you mean you've been claiming her as a dependent? A spouse is never a dependent. You just file Joint. She should only be listed in the top section and not in the Dependent section. And have you been entering her SSDI SSA-1099 and withholding on your Joint return?
