When you're immortal, I guess smoking has no health risk. At least she doesn't have to spend money on lighters.

I think it's the other way around, smoking isn't as problematic for mortals because we don't live for very long.

Hmm but if she dies wouldn't she be healthy again when she rebirths?

It depends on how her immortality works.

The Hourai Elixir makes her immune to illness too. That would include any problems caused by smoking. Probably even includes immunity to nicotine addiction.