Wow- Having read this thread, I'm just going to go buy something nice for my wife? Any suggestions? She doesn't smoke, or vape, but reading this I was just thinking about how much she rocks. Never hassled me about smoking. Wasn't too enthused about vaping in the beginning, but as we learned about it, she's become a fan. (Just got me a mod for my b-day.)
OP- I think with your fiance, you're dealing with a lot of denial and projection. You've quit the cigs. She can't (yet). She feels bad about that (which is normal). It's hard to deal with feeling bad, so...what if she's right, and you're wrong? By finding fault with your vaping, she makes herself "less wrong" for continuing to smoke. It's all totally normal, but a pain in the ..... Not much you can do, though I agree with others who suggested leaving vaping gear around where she may try it while you're out. Don't be obvious, though. Be patient, and SUBTLE. And be patient with the situation, too. New stuff takes time to get used to. Once you vaping is not so new, it probably will stop provoking fights.
To the woman whose BF doesn't like the smell, and doesn't want her to do it in HER HOUSE:
You've got yourself a grade A controlling jerk on your hands. Doesn't like the SMELL? Jesus. There's not much smell. People use perfume. People use soap. People fart. Does he think he has the right to control these, in your home??
Seriously- this sounds less about vaping, more about guys who like to control. Personally, I'd blow vape in his face.
Best of luck to all,
Ande