I am not sure about the third character -_-
Aoko Aozaki or Azaka Kokutou?

I'd say Azaka, based on the eyes.

Unlimited Smoke Works?

smoking is dangerous for the health

I know Rin is a canon smoker, but when did they mention that Ciel smokes?

She's the one with the least reason not to -- it's certainly not detrimental to *her* health.