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.