You might have very good intentions, and I know you don't want to hear this, but you're going about this the wrong way, as many here have attempted to tell you.
I have kicked analogs after 30+ years of using them. I tried everything from patches to gums to hypnosis to acupuncture and everything else in between. Nothing worked until I tried a tank-based system; like the EVOD kit that was linked by another member. I had tried cartos (the simple Blu like ecigs) about two years ago and they did not work for me. I went back to analogs. My parents gave me a similar ultimatum as you gave your girlfriend. That did not work either. I would hide the habit from them and that got to be very stressful for me, causing me to smoke more when the opportunity presented itself.
The tank-based systems, IMO, has the best taste and that is what got me to quit analogs. Different devices work best for different people. Being that she has tried the carto based cig like devices, I would encourage her to try the EVOD kit. It just might do the trick. And, it really is not complicated at all to use. Get her a sample e-liquid pack from Halocigs. I love their juices. I've tried may others and I keep going back to Halo juices.
Most of all, I will tell you to love her as she is, with all her failings. Be supportive of her, if and when she decides to quit. For her to succeed, she will need to make the decision to quit all by herself. Nobody else can do that for her; not you, not her friends and not her parents.
Wishing you both well. I don't recommend that you start vaping and I hope that she manages to quit analogs, even if that means that she switches to vaping. Tell her join ECF and we will all guide her through this.