I actually did miscarry due to quitting cold turkey. That's what my doctor said more or less happened. I thought I was doing the right thing but going from a pack a day to nothing was a bad idea. I genuinely night myself two packs of smokes with this baby when I found out, on top of the full pack I had and decided that when the third pack was gone I was done. NO MORE. So I started baby sitting the last pack and only having one a day till I just quit. It worked for me. Also, I didn't know this then but they have hookah pens with 0 nicotine and 0 tar. 100% SAFE for mommy and baby. God luck to your friend.
I've never heard of that actually happening, but i suppose there is a chance, honestly i used that as an excuse to keep smoking its like justification of the addict :/ when i write cold turkey it was the only way and its not that stressful its just the mind set you use going into it. Whether you doubt yourself or not, confidence is key!!
Quiting cold turkey can stress her body out, and cause her to misscarry, especially if she's a heavy smoker. Have her cut down until she's not having any. I'm still in the process of quitting because my doctor told me that I could miscarry if I just quit, your body is addicted to it the withdrawls and stress from quitting could be harmful.
Quite literally the only way to quit us cold turkey, she can try anything she wants to but yeah...sorry :/