Is it permissible to name a girl "Lُdūn" - with a dammah over the "dal" - intending the meaning of softness, and is naming her with a different name considered a mistake that necessitates change?

There is no objection to naming a girl "Ladun" or "Ludn," whether it refers to the verb, noun, softness and flexibility, or adverb; all these meanings do not contradict the Sharia prohibitions. Therefore, there is no need to change this name.