Access to information should not be confused with entitlement to it.

Knowing something exists is not a claim on the details. People often feel that once they have caught a corner of a situation, the rest is owed to them, and the sense of entitlement is genuinely felt rather than manipulative. That does not make it correct. Information about your life belongs to you and is shared at your discretion.

When someone presses for more because they already know part of it, you can acknowledge the fact and decline the detail. A calm sentence about not wanting to go into it is enough. Repetition is more effective than explanation here.