I decided that I would have to play my character as a very straightforward kind of gal and slightly naive about how relationships work among non-Dalish. She was initially interested in Cullen, Solas and Blackwall, but quickly noticed that the latter two were much more receptive to her advances, so she focused on them. Skyhold comes along and almost immediately she finds Blackwall suddenly digging in his heels, throwing up red flags all over the place and saying, "We can't do this, it's wrong for [unspecified reasons], we should just be friends." Huh. Well, okay, if that's how he wants it... must be a human thing... over to Solas then! And what does Solas do right after almost kissing her to death in the Fade? "We can't do this, it's wrong for [unspecified reasons], we should just be friends." 
At that point she was completely, utterly confused and a little bit heartbroken. She wasn't about to go after anyone who didn't 100% want to be with her, no matter how attractive they were. Meanwhile, she'd been working steadily alongside Cullen (helping to train his archers) and had come to really admire and respect him; eventually she realized that here was a man who would never, ever string her along the way the others (seemed to) do, and decided to take a chance on this "romancing an outsider" business just one more time... and voila! I also had her slowly realize that she wasn't ever going to be able to go back to the Dalish life she once loved, so when the "together forever?" issue came up she felt free to commit to Cullen, Andrastianism and all, though she didn't give up her own beliefs.