Dear Prudence,
I am a law student. A professor invited the students that she mentors out for a drink. However, the law professor left without paying for anyone's drinks. I found this to be rude since she invited us and is obviously in the better financial position. What do you think?
—Law Student

Dear Law,
It may have been thoughtlessness, or the professor may have felt the pleasure of her company vitiated any need for her to actually play host. The bar of justice, alas, is not the bar where you all met. For the future you might bear in mind the concept of "caveat invitee." And whereas this woman may be a fine mentor, "Experientia docet ..." which translates as "Experience is the best teacher."
—Prudie, learnedly