SSDI (Social Security Disability Insurance) is for individuals who have a qualifying work history and have paid into the Social Security system, while SSI (Supplemental Security Income) is a needs-based program for those with limited income and resources, regardless of work history. (AI generated summary)
So if you are asking about SSDI, your wife earned that from her work history and filing a joint return will not reduce the benefit, although it will likely be partly taxable based on your total combined income. (However, the benefit will also be taxable if you file as married filing separately, because if you file MFS then she must file MFS and the benefit is automatically taxable.)
But, if you are asking about SSI, that is need-based, and her need would likely be reduced now that you are married. In fact, if this is SSI, she was supposed to notify the social security administration that you were supporting her once you got married. So her benefit should be reduced based on her marriage, regardless of how you both file your tax returns. Failing to tell the social security administration that her financial situation has changed, could be considered benefits fraud.
