It means she embroidered Military Uniforms.
From "A Dictionary of Occupational Terms"
Embroiderer, embroideress: sews over a stamped pattern or otherwise ornaments, by hand, sewing with needle and silk, wool or other kinds of thread, usually of various colours; sometimes specifically designated e.g. military embroiderer, masonic embroiderer.
Embroiderer, gold; embroiders with fine gold wire threaded through an ordinary sewing needle, by hand or cornerly machine, on to cloth or other groundwork, according to pattern.
Stan