Kiara may be a noble, but she has lived a good part of her life outside her family's influence, living under her own assumed name as a rogue and thief. (This was before I even knew there was a Blackwall, so, these two were totally meant to be!). As a child her best friend and first love became a mage. They'd tried to keep it hidden, but it wasn't something that could be hidden for long. He was taken away to a circle, at the height of their crazy mad us-against-the-world love that only those just out of childhood can sustain. It turned her against the family and the chantry as a whole, since she blamed them for it. After this she made disastrous choices, first to get back at the family and then later because that was the lifestyle she'd gotten herself into. When the last affair had taken a heartbreaking turn both personally and professionally, she decided to stop straddling two worlds and return home for good. It was time to make amends with her family, give up on the idea of love, and use everything she'd learned for the betterment of her family. She volunteered to go the the conclave, and her family decided to give her that chance, as she would be the one most likely to learn any secrets they could use to further their line. Instead, all hell broke loose.
When she met Blackwall, she was still determined to believe there was no such thing as love. She felt an immediate attraction to him, and when he not only saved her from the arrow, but was so sure of himself and commanding and wonderful in the fight, it may have made her knees go a little weak. But she thought she could both like him as a person and lust after him as a man, without falling in love with him. Maybe she would sleep with him, and maybe she wouldn't. She may have given up on love, but that didn't mean she couldn't flirt and have a good time.
When she saw him in the future Alexis sent her into, how he looked at her through the gates of those bars when seeing her alive and how he sacrificed himself to give her the chance to get back through the portal -- she started to suspect it was more than infatuation. Still, she wasn't ready to call it love. Then the attack on Haven happened, fighting a dragon and a darkspawn claiming to have seen the seat of the Maker. Fighting, and surviving. Again. The trek through the snow, the complete faith of the people ringing all around her, skyhold rising out of the mountains... all her beliefs were shaken. Maybe she'd been wrong about Andraste, about the Maker. If she was wrong about something as big as that, maybe she was wrong about love too?
Everything felt as if it were rushing out of control. The people's belief, being made inquisitor, everyone looking to her for answers. This is when Blackwall took her up to the battlements, and tried to get her to step back from their relationship. The relationship she'd been telling herself didn't exist, it was only flirtation. And this, this made her laugh. Because she suddenly realized he was as afraid of love as she was, and she knew with utter clarity that he had something in his past he felt made him unworthy, just as she did. With his fear, she felt less afraid. As if by him trying to run away from the problem, it made her want to step up and face it. She wasn't ready to admit to being in love at that point, but she was open to the idea. Every day he proved himself to her, proved how unlike he was from any man she'd been with before. Every time he said, "my lady" and meant it, her mind opened a little more to the idea of love.
Later, after they retrieved the badge and he'd come to her room, he kissed her. And then he'd more than kissed her. In the dark, in the night, while he snored like a bear, she'd thought, maybe I love this man. Later still, somewhere on the Storm Coast, after an exhilarating fight against a small horde of darkspawn, still breathless from the attack, not from exertion so much as from the high she got whenever they fought in tandem, Blackwall had reached for her. Wiping the blood from her arm with such concern, he'd asked if she were all right. There was both fear and love in his voice. She came to two realizations at that point. He was no grey warden, and, yes, she loved him.