I sometimes hear that Catholic women should imitate the Blessed Mother in dress, or that we should ask ourselves if we are dressed in a way in which the Blessed Mother would have dressed.
I think there is a conflation here of two different concepts: imitation and mimicry.
Imitation is using someone or something as a model for one’s own actions;
mimicry is to attempt to create an external, superficial resemblance to something or someone else.
Too often in discussions of modesty, it seems that those advocating for using the Blessed Mother as a role model confuse mimicry for imitation. That is why you sometimes hear then of Catholic women who don’t cover their heads in church or elsewhere, or who choose to wear pants, or who do not cover every square inch from neck to toes, denounced as “immodest” for not following some perceived “Marian code of dress for Catholic women.”
We are not called to be mimics of the Blessed Mother, dressing as would be appropriate for a first-century Palestinian peasant woman (e.g., long veils, skirts to the floor, sandals). We are called to imitate the Blessed Mother in her virtues. In terms of modesty, that might mean dressing in a way that is appropriate to one’s culture, not drawing undue attention to oneself either in one’s dress or undress, and remaining circumspect about one’s own choices and not denouncing the reasonable choices of others.