So you've decided to embark upon a romance with Dragon Age: The Veilguard's freckled scout, Lace Harding. Congratulations. You've made the best choice. A relationship with Harding has a lot of things going for it. She's fun without devolving too much into MCU-style banter, she's tough as hell, and her storyline is one of the more compelling ones.
Harding also makes more sense as a paramour. While the rest of your companions are strangers to you, Rook and Harding have been buds for a whole year by the time the game kicks off. And if you've played Inquisition, you'll already have spent a bit of time with her—albeit as a different character—in her role as Inquisition scout.
Good news! Like most characters, you have to actively avoid Harding if you don't want the option to develop your relationship with her. She doesn't have a faction, unlike every other companion, but simply using her during quests and picking flirty dialogue constitutes the bulk of your task if you want to get a date.
One thing to note: increasing your bond with a character does not contribute to your relationship status. What it does is unlock their personal quests, which often give you opportunities to flirt, and that's what puts you on the path to romance.
Harding wants some help getting a handle on her new abilities, so the two of you go on a field trip to move some rocks around. There's not much to this quest aside from some terraforming, though you will get a flirty dialogue option.
This will set you on the path to a romantic relationship, and you'll have a cute (if a bit chaste) scene where you snuggle a wee bit, before you mysteriously start to feel a bit woozy. At this point, you can still continue romances with other companions, so you aren't locked into anything.
This is where you become an exclusive couple, setting tongues wagging in the lighthouse. You'll need to visit Harding in her room after continuing to develop your bond, and she'll ask you to join her in the Halls of Valor, starting The Bond Rekindled.
While you're hanging out in the Lords of Fortune's stomping ground, she'll express her worries about her newfound power, and you'll get a quartet of supportive responses. Despite them all broadly having the same tone, three will end the relationship and one will commit to it. Which is which is clearly marked, but you should choose:
And there you have it. You are now in an exclusive relationship with The Veilguard's best companion. There are, naturally, more romantic encounters, especially since there are certain obstacles getting in the way of your happily ever after, but by this point you're locked into the romance.
Before you deal with the final Big Bad, you'll get your classic BioWare "Let's have a steamy night before we risk our lives one last time" scene. And like all of The Veilguard's romantic moments, it's extremely chaste, with a only a smooch before you get the fade to black. Then you're on the sofa in your underwear having a heart to heart.
And that's pretty much it for your romantic encounters, with the exception of one scene right before the end where Harding briefly plans her future with you, before you march off towards the final confrontation.