I'm not sure what 2018 nor the status of my mother's filing has to do with the question.
Clearly it is more beneficial to have her file jointly (as surviving spouse), since that would make here eligible for the deduction for both of them. Additionally, as I mention her spouse's business had expenses which were paid, but no income was earned in 2019 ("accrued" might have been a bad choice of words as it confused "accrual accounting" with "cash").
So, in addition to filing a joint return, it seems feasible that she should also be allowed to file a Schedule C for his business to indicate his losses (expenses but no income).
I just want to ensure this wouldn't raise many red flags.
