As I mentioned earlier in this thread, Darci becomes available after the Yacht event, and as
Zane11 mentioned you'll need to complete the Robotics lab, which means you'll need to track down some parts for said Robotics lab (read: heists). Then, once the lab is completed, you should run into Darci chasing Toyman in the Villain's Hideout.
This is covered in Archer's guide, and I also briefly summarize this in the Quick Reference sheet that I made that is also linked in the OP, which I updated this morning for 2.3.7. Both references can be rather helpful in helping figure this stuff out, for those that don't grok developer logic...
There was another guide that I found rather helpful as well, but it hasn't been updated in years. My quick reference is mainly to give you quick facts like what level a Superheroine is, where scenes happen, that sort of thing, when you just need quick facts and not a full walkthrough for various characters.
ntentacle
Have you completed the progression with Darci in her cell? I'm guessing you need to get to a certain point with her before she's willing to gift Lana to you. I had reached the 'nickname' stage with Darci in 2.3.6, and had no problem using that save to trigger this event in 2.3.7 when I picked up where I left off.