If all of you live in a 2 bedroom basement, I do not think your mother can stay at the basement to quarantine unless all 5 of you will be staying home for the 14 days. ( no school, no work, no grocery shopping)
I think it's better to get her an air bnb rental or a hotel room for quarantine. You can drop off supply to her at her unit's front door. (do not go inside or have any physical contact)