Tell her, the way you would tell a colleague: 'Heidi, remember that Acme's renewal moved to March.' It becomes a fact with you as the source, permanent until corrected, and it shapes every future answer it touches.
Direct teaching is the fastest path into the brain and it needs no ceremony: state the fact in chat, in her own interface, or over the API. She confirms what she stored, so you can catch a misreading immediately.
The high-value things to teach are the ones no system records: preferences, unwritten rules, context behind decisions, 'never deploy on Fridays,' 'this customer's champion left, tread carefully.'