To be honest, you'll have to do the work yourself. I went through 200 of the over 650 pages of widowblinds (starting from oldest) without finding the skin..... if it's there, you'll find it eventually.
There is a clue there in your shot if you look closely. The folder in the picture says Alexandrie's Documents leading me to think it was a Pixtudio skin......although I'm not sure if she ever released skins under her own name or something other than Pixtudio.