This was enunciated in a scene in GUZAARISH where she was required to smoke.
Here the scene required Aishwarya to smoke and in a fun manner.
It shows her with Hrithik Roshan in a car. Aishwarya takes a puff and immediately starts coughing. Hrithik cannot stop himself from laughing, which gets Ash giggling too.
The 36-year-old actress has never smoked in her life so it was a first for her but she indeed pulled it off very well. And the scene has come out perfect, just what the doctor ordered!