You're right, Très Chic needs Crit Rate much more than she needs Accuracy. By default, she has a 100% chance to apply a debuff when she crits, so Accuracy will only have an effect if the opponent has built Resistance. More Crit Rate, by comparison, will always result in a higher rate of applying her debuffs to a non-Immune target, with the added benefit of getting consistently higher damage output once she applies Death Mark.