Why Didn't Lucien Deserve a Warning?

Why, upon discovering Ianthe's unscrupulous actions through Rhysand, did Feyre not show deeper concern for the damage Ianthe might still be causing in the Spring Court — especially with Tamlin and Lucien trapped in her manipulations? While in the Spring Court, Ianthe's behavior unsettled her, though at the time she couldn't fully discern why. So why, when she realized she had been manipulated and disturbed by Ianthe in the past, didn't she consider the possibility that Lucien/Tamlin might also be a victim of the priestess's schemes? She acknowledged the possibility, imagined that Lucien could be ensnared in Ianthe's web just as she was, but felt no urge to act? Why did she only send a cold letter to end things with Tamlin and not spare a single word to warn Lucien about the danger he was in? Lucien, who had been an ally, who deserved at least a warning — why nothing? At any point in the book, does she reflect more deeply on this? I'm currently halfway through A Court of Mist and Fury.