Which lady specifically? (I'm sure you said but don't remember now).

Plaid particolored lady looks like there is a white-leyer cuff line on her right wrist but not her left.

None of the other women, except for the Holy Mother seem to have an underlayer of any type.

My vote is that it's a short-sleeved or sleeveless chemise, of which there are images available (dunno about short sleeves in Spain tho'!) for England and France.