Through your journey, Astrid and Giovanni will join your ship. Their storylines are directly connected up to the ends of their journeys. Toward the end of their story you will unlock two quests, "I Have My Doubts" and "Indiscreet Meeting". Complete "Indiscreet Meeting", by taking Giovanni to Oxbury and then follow and spy on him while there. When you return to the ship, save and quit the game before talking to Astrid. Reload and talk to Astrid. You can choose to tell her the truth or lie about Giovanni. After choosing one of the options, you will earn either Loose Lips or Sealed Lips based on your choice. Then reload your save and talk to Astrid again, choosing the other option to unlock whichever achievement / trophy you didn't unlock the first time.