Electronic Cigarettes May Not Help Smokers Quit
A small study done by The Center for Tobacco Control Research and Education at The University of California, San Francisco, suggests that e-cigarettes don't actually help people to quit smoking." Of the 949 smokers in the study, only 88 used e-cigarettes, causing the study's researchers to "admit that their findings should be viewed with some caution."World Science reports "They also found that e-cigarette use was more commmon among women, younger adults and people with less education." Last year, the US Centers for Disease Control reported e-cigarette use more than doubled among U.S. middle and high school students from 2011-2012. The lack of solid research, potential youth market, and abundance of caution have had anti-tobacco activists and researchers pushing for a ban on advertising of e-cigarettes.
NPR has a recently story about vaping, or using e-cigarettes, indoors and in the workplace.
If you smoke, have you been able to cut back your smoking or quit thanks to electronic cigarettes? If you do not smoke, does it bother you that others use e-cigarettes indoors?
You point out that proylene glycol is "potentially dangerous". It is used in and approved for several food products, toothpaste and cosmetics. Not safe for inhaling? Well, it is used in smoke machines too, which have been around for decades and have not been proven harmful. The only difference between an e-cig and a smoke machine is the nicotine (not detectable in an 8m^3 room) and flavorings (does not stink like cigarettes).
There are even some indications that PG might be healthy (from a quick Google search): http://www.news-medical.net/news/20091104/Propylene-glycol-in-e-cigarettes-might-keep-us-healthy-says-researchers.aspx
Vegetable Glycerin is also widely used in e-cigs. It is hard to come across any candy or sweets which does not contain it. It is basically sugar.
I think your mom's behaviour is unpolite, to say the least. It is not a question of wether e-cigs are dangerous or not, but of manners. E-cigs are not subject to smoking laws, at least not in Norway, but you got to respect people around you.