"I do not think there is enough time in the world to prepare me for that." She responds, casually and with a wave of her hand. "But I know what I must do, Solas, if I fail to turn you from this path. Do not doubt my resolve." Perhaps not the best thing one could ever tell the man she loves -- that she will kill him should he force her hand. But it is the truth -- Thedas has more value, more weight, than her feelings for Solas.

She's sacrificed everything else for it, what would be one more thing?