Period art that portrays cantinieres often makes them as the center of the picture. I wondered if cantinieres were really with the troops or added for color by the artist. I came across some period art that features a figure of a cantiniere in a military setting and I've circled them. My "theory" is that if they are shown as part of the scene, they were really there rather than added for color. The scenes below are depictions of the Paris Commune 1871.
French POWs after the defeat by the Prussians.