How will you punish her?

By instituting a system of nudity punishments

You stare at your grad-student until she starts to squirm under your disappointed gaze. She has to be punished, that's for sure, but a quick spanking, soon forgotten, no matter how painful in the moment, may not be the best solution. Then her embarrassment gives you an idea and you order her to stand in the corner, with her nose against the wall. She obeys with alacrity, but you can tell from her deportment that she's finding the childish pose humiliating. Now to harness that humiliation in the cause of greater discipline. You take out the Rulebook and start to write.

Old Rule: Nobody ever takes offence at any punishment given to a woman of spankable age.

Old Rule: Women who are punished must go about their usual business regardless of any discomfort caused by the punishment.

New Rule: Women of spankable age may, instead of or in addition to a spanking, be punished by a period of enforced full or partial nudity. Such women must wear a placard, proclaiming her offence and the duration of her punishment. If other clothing is required for safety or practicality, then it may be worn, but in such a way as to minimize the privacy it offers. Special safety equipment is widely available to maximize exposure and humiliation.

New Rule: Whatever a woman's usual attitude to people seeing her body, a nudity punishment causes utter mortification.

That should have the desired effect, but for purely practical reasons, you add something to the college page.

New Rule: All staff members, regardless of age or gender, have been issued with a number of placards which they may use to instigate the nudity punishment of students. These should only be used on rare occasions when a nudity punishment is thought to produce a better result than spanking or spanking alone.

You check the drawer where you would keep such placards if you had them, and sure enough, there they are, a dozen of them, just waiting. Trish is in for a very embarrassing few weeks, but perhaps she needs more than that.