Encouraging and supporting her is the best thing you can do. If she is truly ready to quit, she may just need a little help. I used the Patch, and it worked well for me. She may get bizarre cravings, I "needed" coffee - a lot!

So, if cold turkey isn't cutting it for her, there are many options - the patch, nicotine gum to name two.

edit: Forgot to add - 14 years since I quit!