I was at a SSPX mission, and this young man brought a female companion who was showing her cleavage and wearing sleeveless shirt. She took Communion and the priest didn’t say anything.
So when and where did the priest see her for the first time? at the communion rail? Not the appropriate time to admonish/instruct/center out anyone on their first time visit.
If you saw her before Mass did you offer her a sweater or ask if she had something to cover with? Or if the young man was a regular, did you take him aside and encourage him to rectify her error?
Not every situation can be resolved to a charitable/satisfactory outcome on sight.
Remember, the bible says to admonish the sinner once,
then admonish the sinner with another witness,
Then take the problem to the priest.