Those are great ideas. I also have a barker and I apologize to my neighbors all the time. They tell me they don't hear her. Or if she does bark out of control they simply say her name and talk to her and then she stops. I gave my neighbors permission to tell her to shut up! LOL He said talking to her helps. That way she knows who is out there.
Maybe the neighbor that needs to sleep could meet Mindy and then she'd know them and quiet down when they tell her to. That's a stretch, I know.
Too bad Mindy and the other neighbor dog couldn't hang out together during the day. Or can they?? Then she'd have someone to play with and keep her busy. And it would only be the days she isn't at doggy day care.

I don't know, just throwing ideas out there. There is also a device called Bark Off. We got it and we can't use it for Zoee because she is so sensitive that it freaks her out. My mom has one and it doesn't seem to work for her dogs either.........AND my mom and niece can hear it!!! So I wouldn't waste money on that device. But it does work on some dogs, just not mine.

Good Luck!! And thanks for the picture of Mindy.