Yes I do mention DS as well, though not a great deal. I also mention him from time to time when I'm teaching, as I think it's quite important that the students see that women as well as men can have a family and be enjoying their job and not finding the juggling too impossible, or at least finding it worth doing. Sounds obvious but there is no other woman in my (quite large) department in that bracket.
NK these situations are v. difficult in academia because as you say there is rarely any clear chain of command, and also there are essentially no repercussions, except in general career/reputation terms - and that's often a much more important factor for one person than other (e.g. more established) contributors. Could you say something like - sorry you are still stuck on the ending of the article, I always find endings difficult too; I would really like to submit it by [realistic but soon date] though. Do you want to get together on Friday morning to spend an hour putting the finishing touches to it together?
This is friendly but serious, and might shame her into either finishing it and sending it yourself, or at least agreeing to the meeting (which I appreciate takes up more of your time but would at least move things forward, and might tacitly give you permission to take over and sort out the problem).
If that doesn't work I think you just have to accept that it's stymied for now and try to let it go so it's not using up emotional energy; as you're not lead author you can't I think just insist on finishing it yourself.
Although it is infuriating I do think it is worth keeping your temper in these situations, if only because academia is so small and the person you get cross with is bound to be asked to review your work or an application at some point. And also I have found that most people (though not all!) do appreciate and remember when you are patient and professional and that can reap rewards eventually - they will feel like they owe you.
I have a similar situation at the moment. I am editing a very large book with around twenty-five mostly very senior contributors from around the world. All the chapters have now been in for over six months (and some came in a couple of years ago, due to staggered deadlines) but I am STILL waiting for the second half from a certain v. senior German scholar who is now around a year late. It is driving me absolutely mad because the entire project is held up just for him - and I really wanted it finished before a second pregnancy because I know I will be out of action - and there is essentially nothing I can do about it - the pay for these things is so incredibly negligible as to be insignificant; his reputation is already secure; if I dropped the chapter the gap would be very obvious; and there is perhaps one other person in the world who could do a decent job on this topic, and I asked him first!
I have felt better recently though after sharing this problem with a colleague in Austria editing a fairly similar volume. It turns out that he has three such offenders (which makes me feel like a successful manager!) and also we shared our list of problem contributors so as to pool information about who not to ask in the future! At the same time this has reinforced my good working relationship with this colleague, who is more junior than senior German but is undoubtedly going to be one of the two or three leading scholars in the field within ten years (hopefully I'll be another of them!).