She likes him. She's not going to deny it to herself. Even if she tried, Adaar would just tease her mercilessly until she fesses up.
So, she likes him. That's obvious. And, apparently, it's obvious to even her companions, despite all her attempts to downplay it in public. Only Lavellan and Cadash would outright confront her on it, of course, but it's embarrassing seeing the knowing eyes and smiles.
Why doesn't she say anything? That's… that's also obvious. At least, it is to her. Because he'd been in love before, with a beautiful mage called Amell, who later became the Hero of Fereldan. And Varric's stories would always talk of his close friendship to another gorgeous mage, Hawke, a scion of the Amell family.
So, how could she compare? She is drab, mousy even. And a mage, meaning it would nearly be impossible not to compare herself to the two heroes. Especially when she is floundering about after the other three Inquisitors (as Cassandra 'lovingly' dubs us four).
She might be the Inquisitor in charge of the spies, but she has just enough pride to not be anyone's second place… and to keep herself out of another's shadows for as long as she can. …Even if it hurt.