Hypnotism works when you -want- to be hypnotized. If you just sit there not expecting to be hypnotized then you won't be. Since her mom wanted to stop smoking, I assume, then she gave into it. So yes it can work when you want it to, but it's not like there's people out there who can sit you down for twenty seconds and have you barking like a dog the rest of your days or something.

Oh yeah, regarding quitting smoking, chew the nicorette if you have to but you will have to go cold turkey eventually.