Note: there are probably better options to unlock this, but these are all the dialogue choices I made to unlock the achievement.
Set your career as Other, your interests as Spirituality, Arts, Charity, and your astrological sign to Cancer.
First Date
-Running
-Modest
-Vegan
-Books
-Poem (Note: The Planting the Seed achievement will unlock here)
-No
-No
-Why?
-Yes
Second Date
-Moon
-Upright
-Engage
-2 of Swords
-Upright
-Engage
-7 of Cups
-Upright
-Engage
-Stay (Note: the Not Alone achievement and the most embarrassing scene in acting history will unlock here)
Third Date
-How long have you had them?
-Quality time
-Yes
-Long distance
-Challenge
-I'd like to keep seeing you
Achievement unlocks after the credits, which you can skip with RB.