In Back to the Future Part III, after the festival, Clara is showing Doc craters on the Moon through her telescope. Afterwards they start talking about their favorite writer, Jules Verne. Then they kiss and the scene ends.
The next morning Marty realizes that Doc is missing. Did he spend the night with Clara at her house? If yes, then it appears unseemly for a woman in the 19th century to sleep with a man on the first date, doesn't it? She probably risked her reputation as a teacher.