And remember what John said, hardened leather protects very well, is relatively lightweight and sits nicely on top of padded protection. I vote to see if she's interested in the greco-roman style of heroes, generals and emperors before you go full-on "Nope." =)
EDIT: However, I can understand if you feel that you've done what you can for her, I urge to one last shot at making her more period, a roman amongst them barelycelts (or what you called them) would certainly be quite a nice suprise to maybe wake them out of their fantasy-armour-ways
But once she's done, she's done. Hand her off, in a nice way, to a marshal or similar to discuss further armour ideas and see what they can come up with for legality and protection.
