What advice did she give regarding keeping information private?

The answer captures an informal expression that conveys the same meaning as the advice to keep information private. "To keep it under her hat" is an idiomatic phrase that suggests one should keep certain information confidential or secret. This aligns perfectly with the idea of maintaining privacy regarding information. Such idiomatic expressions are particularly effective in conveying nuanced meanings in a casual context, emphasizing the importance of discretion without directly stating it.

The other options imply sharing or discussing information rather than keeping it private, which contrasts with the intended advice. Sharing or discussing information openly does not align with the notion of keeping something confidential.