Note: there are probably better options to unlock this, but these are all the dialogue choices I made to unlock the achievement.
Make sure to set your astrological sign to Cancer for her.
-Poem (Note: The Planting the Seed achievement will unlock here)
-2 of Swords
-7 of Cups
-Stay (Note: the Not Alone achievement and the most embarrassing scene in acting history will unlock here)
-How long have you had them?
-I'd like to keep seeing you
Achievement unlocks after the credits, which you can skip with RB.