I haven't completely switched off analogs, so I don't know if I am the right person to give an opinion. Also, I am trying to make the switch while I have a cold with a nasty cough. But here goes anyway...
I would say try to work it in gradually. My goal is to cut down on analogs to the point of making a final switch, but I have not put myself on a time line and this was my idea not my husbands (maybe that helps LOL). I have had the coughing problem sometimes, sometimes because of the cold but other times the e-cig does give more of a throat hit. Maybe if you could find a way to make it fun so she doesn't feel any pressure or expectations. Has she joined Vapor Talk? Sometimes talking to someone other than your spouse helps. I try to tell my husband something he isn't all that jazzed about it, but if he hears the same exact thing from someone else all of a sudden it is the greatest idea.