floursack

A sack for flour.

She brought us her quilting scraps in an old floursack, ready to be used in our crafting project.

Sackcloth. (In the nineteenth and twentieth centuries, floursack cloth was often reused for making clothing, quilts, or rags, and this tradition continues to some extent today.)

Near-synonyms: hessian, burlap

Let's be honest: the outfit hardly matters — you could put her in a dress made of floursack and she'd still look fabulous.