It was probably made up by someone who doesn't get attention at home and wanted to appear interesting.
Yutaka Huemura also spoke about it with WebNewType and, as the anime's director, wanted "each character's design to reflect their character and personality."
That's a hoax. The author didn't ask for anything regarding the character designs; that's just Yuuji Hosogoshi's signature drawing style, and you can see this from his previous works. According to the WebNewType interview from february 2017, Carlo Zen didn't want to be too involved in the...
JP to SPA translator here.
Yes, you're correct. "White Silver" is her official alias, but she's rarely referred to as "Silver Wings" in the manga, and also as "the one with the silver wings". Mangaka sometimes alternates these names.