Actually her armor was made from a Naboo yacht that once belonged to Palpatine, hence the silver/chrome look.

As for Smith, that was a rumor but was never officially announced and Matt Smith himself said it wasn't true. It's possible Smith might've read for a role in the film, as many actors do. Jessie Plemons for instance read for one of the roles in TFA, possibly Finn, Poe or Ren, but was not cast.