Let's look at what St. Thomas actually wrote. Here you can find the entire question in context, something that our Puritan troll fears.
http://newadvent.org/summa/3169.htm#article2Nevertheless a woman may use means to please her husband, lest through despising her he fall into adultery. Hence it is written (1 Corinthians 7:34) that the woman "that is married thinketh on the things of the world, how she may please her husband." Wherefore if a married woman adorn herself in order to please her husband she can do this without sin.
Notice, "without sin", not venial sin as the dishonest troll keeps saying.
Now, let's keep going in that paragraph:
And if indeed they adorn themselves with this intention of provoking others to lust, they sin mortally; whereas if they do so from frivolity, or from vanity for the sake of ostentation, it is not always mortal, but sometimes venial. ...
Yet in this case some might be excused from sin, when they do this not through vanity but on account of some contrary custom: although such a custom is not to be commended.
Again, "excused from sin" period.
Now his reply to one Church Father (St. Cyprian) who wrote against cosmetics:
Reply to Objection 1. As a gloss says on this passage, "The wives of those who were in distress despised their husbands, and decked themselves that they might please other men": and the Apostle forbids this. Cyprian is speaking in the same sense; yet he does not forbid married women to adorn themselves in order to please their husbands, lest the latter be afforded an occasion of sin with other women. Hence the Apostle says (1 Timothy 2:9): "Women . . . in ornate [Douay: 'decent'] apparel, adorning themselves with modesty and sobriety, not with plaited hair, or gold, or pearls, or costly attire": whence we are given to understand that women are not forbidden to adorn themselves soberly and moderately but to do so excessively, shamelessly, and immodestly.
and
Reply to Objection 2. Cyprian is speaking of women painting themselves: this is a kind of falsification, which cannot be devoid of sin. Wherefore Augustine says (Ep. ccxlv ad Possid.): "To dye oneself with paints in order to have a rosier or a paler complexion is a lying counterfeit. I doubt whether even their husbands are willing to be deceived by it, by whom alone" (i.e. the husbands) "are they to be permitted, but not ordered, to adorn themselves." However, such painting does not always involve a mortal sin, but only when it is done for the sake of sensuous pleasure or in contempt of God, and it is to like cases that Cyprian refers.
It must, however, be observed that it is one thing to counterfeit a beauty one has not, and another to hide a disfigurement arising from some cause such as sickness or the like. For this is lawful, since according to the Apostle (1 Corinthians 12:23), "such as we think to be the less honorable members of the body, about these we put more abundant honor."
So if a woman has blemishes or acne or other skin issues, NO SIN. Notice how his reasoning echos that of the priest quoted in the OP.
And, finally, ...
Accordingly, since women may lawfully adorn themselves, whether to maintain the fitness of their estate, or even by adding something thereto, in order to please their husbands, it follows that those who make such means of adornment do not sin in the practice of their art, except perhaps by inventing means that are superfluous and fantastic.
"lawfully", i.e., without sin.