I'm in a similar position as my fiance is still a smoker with no desire to quit. I think she is a little interested in the eCigs now that I have gone over 3 weeks without touching an analog but she will be a challenging convert.
Analogs are still cheap in Belize and there are not to many places where smoking is not permitted.
Even the 510 I'm using is too big in her opinion and she is a 2 pk a day smoker so I don't think a mini will be ideal for her anyway.
She doesn't like the weight of my 510.
She is generally resistant to any change in routine.
She definitely will not be interested in refilling anything (at least at first) and cartos can't be bought here in Belize which means either expensive shipping and customs charges or packing a boatload of cartos the 2 or 3 times a year she is in the US.
Any and all suggestions are welcome! So far I am thinking a k808 system with refillable cartos and plenty of batteries might be my best option as long as I can be around to refill for her when needed.
If she feels your 510 is too big she might be happy with the kr808s of the ones out there I like the Volt from Smokeless Image They have gotten some very good reviews - the battery life isn't perfect but they vape like a champ!
http://www.e-cigarette-forum.com/forum/e-cigarette-suppliers-forum/187974-official-smokelessimage-com-thread.html