My mother receives SSA check only; How to fill the 1040A form so she can get a stimulus check?

I am filing taxes for my mother in law - are both ssi and ssa taxable income?

What do social security benefis include when filing Form 1040 A ? Do they mean both SSA and SSI, or SSA only ?

I recd an SSA-1099 for my social security (disability income). Does this mean I can't just do a short form? I do not make enough to owe taxes, but I am told I have to file anyway just to get my rebate from the govt so this is my first time to file.