Holy crap (har!) I think we've done it! Delphinium showed some interest out of the blue and we seized upon it as enthusiastically as we could. A few times since then she's asked for diapers, but we just keep saying that she's a big girl and only the baby should be wearing diapers. She seemed quite fine with that idea.
The first few weeks were a bit rough. Sometimes, by the end of the day, I was washing an entire load of wet things which was quite demoralizing at times. We did persevere however, and things did get better and better. It helps that we have a travel potty which allowed us to stop anytime and anywhere to have a quick pee. It also helps that we were in the the thick of training over Easter, and I broke my less sugar rule by giving her a jellybean every time she sat successfully. At roughly two jellybeans per hour, I felt it was a worthwhile trade.
About three weeks on, and we're mostly there. I would say that we now average one accident every three or four days, and even that seems to be tapering off. I bought some iron-on transfer patches to help her tell front from back on her underwear, so we talk about trying to keep the robot or the butterfly dry. We have not even attempted to go all night, but sometimes she wakes up dry too, so I have hopes. Now if we can just avoid regressions, we'll be in great shape. Fewer diapers! Squeeee!