Few NPCs will ever initiate; usually you'll need to be the one to initiate, else the subject will assume your relationship is platonic at best.
However, just because you flirt doesn't mean the subject will respond favorably.
All NPCs have their own preferences on partners they want, if any.
Some NPCs, especially non-party members, may react favorably in specific quests, and initiating a one-night stand may resolve quests in special ways.
Each of those eight have specific gender and/or race preferences that you cannot overrule, though you can usually flirt with them even if they won't want to take things to the next level.
Assuming you use flirtatious dialogue options every time you speak to her, Harding will flirt back and even comment on where your relationship is heading once you acquire Skyhold.As the player, you can attempt to role-play a polyamorous character to an extent, but none of the NPCs will reciprocate.You can flirt with as many characters as you wish (subject to their preferences), but as you complete storyline milestones, multiple suitors may confront you and ask you to make a choice.(Of course, if you're role-playing or trying to craft a particular tale, all bets are off!) Note that Josephine and Cullen are not subject to the approval ratings.Unlike previous iterations of the franchise, these numbers are hidden from you.