My kid graduated from a SLAC this year. 8-10 kids graduated from his department. He did research for his departmental advisor, took multiple classes with her, she supervised his senior research, served as a reference and helped him out of a couple jams. He took her flowers with a handwritten note (yes, at my prodding) to the departmental reception. It wasn’t necessary, but they had worked closely for three years and I don’t think it was out of line. She definitely seemed touched.