Do you have to file for taxes if you receive public assistance or welfare?

I never thought into it and my mother hasnt filed in a while becaue she says she was told not to file. I understood it then being that she was not working but now i need college stuff and they need tax info and she says she has none. I ve heard about some form that is available but i dont know what it is, and how u get around the tax thing anyway. HELP ME cuz i need applications done!