Early in the update, Lydia will ask if you truly believe her. Choosing "I never doubted you" provides a significant boost to her romance path.
Lydia is the central figure. In v0.14, your relationship moves beyond the "Client-Lawyer" dynamic. Defending Lydia Collier [v0.14] [APK]
If you're lost, use the "History" or "Log" button to see what evidence you've already discussed; it often hints at what’s missing. Early in the update, Lydia will ask if you truly believe her