As a female who became obsessed with cycling at an early age it's hard for me to comment on how to entice someone into it, however I think creating a link between how she approaches sport maybe key. So if she likes social sport creating links between cycling and being social could be good. The ideas of picnics, massages all sound great to me! Wineries and weekends away with little bits of cycling may also help. If she's competive then spin claasses and a racing club maybe more her style.
I think you may also have to accept that cycling with your GF maybe different to your normal way of cycling irrespective of how much she likes it. She may never view it the same as you - just like anything else.
Something I once liked a lot was a boyfriend who cleaned down BOTH our bikes after a ride telling me he wanted to make sure I was safe out on the road when I went out without him - that worked better than a massage

I traded by cooking a yummy dinner while he made sure we were both safe. Something I dislike is men who hover at the tops of hills waiting or worse looping back down to see how their partner is going indicating just how slow they are (even when by normal standards they're not).
The weight difference in bikes and clunky gear always gets to me too (when i see couples out riding) so perhaps until she gets better (or you upgrade the bike) offer to carry her things to make it that bit easier - you are bike fit after all. Then later when she's more interested she can indulge in some retail therapy by finding her own carriers etc. Rest stops at coffee shops, art galleries, pubs are all great distractions so she doesn't notice the distance but also a great way to build memories of your trips out.