i side with perilus on this one, but to a lesser extent. If she's mad, throwing facts from websites in her face isn't going to help the situation, that can come later. For now, be honest and say that you do smoke, assure her that you are responsible about it, and assure her that you are willing to sit down at a time when she is more level headed and discuss it like adults.

Be honest, be respectful, but don't surrender your ground.