There is pretty much nothing you can do from your end..........sorry.
and only if you get along with the neighbor,
an easy fix to the problem can be that they replace the one board that is making it squeak.
This is done by cutting out the part of the board that sqeaks then replacing it with a slightly larger one,
then screwing it down onto the joist below it.
The reason it sqeaks is because of the constant swelling and contracting of the board and it has weakened.
I have done this and it only takes about 15 minutes to do.
If I can do it being blonde and a woman so can they.