Fun fact; women gladiators are perfectly historically accurate!
They'd fight against other women, but usually it'd be against much more common male gladiators, as well as captive animals and slaves/criminals on death row.
However, due to Shizuya's pretty clearly personified approach to drawing outfits and bodies, this lady's design has a couple of shortcomings:
Firstly, "nipple armour" on women wouldn't work the same as it does on men, as such design requires the entire breast to fit in the, well, breastplate. But because breasts are pretty sensitive (they're mammary ducts and lobules encased in fat pockets) if the fighter were to suffer a fit directly to the breastplate, the metal would actually add to the blow and push on the breast, heightening the chances of fractured upper ribs.
Secondly, the armour itself is plain ol' unnecessary, as these gladiators fought topless! This kind of "bikini armour" would be difficult to make in ancient times, and so the women fought either in men's armour or none at all, much like their male counterparts!