OK ... STOP OVERTHINKING THIS ... if her only income is SS benefits then she has no reason to file an INCOME tax return. If the home health aides are being paid thru a payroll company then the payroll taxes are already being handled so there is NO REASON to file a Sch H at all even if the payroll company was kind enough to give you one filled in ... that info is NOT sent to the IRS thus she has no need to file anything herself.
As to the multiple payroll companies ... it is not unusual to have more than one in a single tax year so if the last company you use will not combine the info for the required forms then you can get the paper forms from the IRS and manually fill them in yourself. Please talk to them afterall you are paying them for this service.
