User blog comment:KnocknickKnock/Lucy Stardress:Crux Form/@comment-1776824-20150520200309

Given that the Star Dress was only introduced a couple months ago and she has performed it with only her gold keys thus far, she just has flat out no reason to perform them with her silver keys since none of them are suited for combat, which is the purpose of her Star Dress: to give her that edge that she never could have before. However, it was also likewise never stated to work on the silver keys too, so it's honestly better to assume that it doesn't. She has no reason to use her Star Dress for silver keys like Crux when Crux can clearly just telepathically hand Lucy the information, or just tell it to her in person. It's pretty pointless for her to do it herself, and at this point, I'm thinking Star Dress is the "secret skill" that makes one the Celestial Spirit expert.