I didn't try out PathFollow but I can tell you how to get the global y-angle for any spatial.
Also, I did some tutorial/text about 3D vector / transform operations:
You should get an angle with this code:
This gets the x and z components of the current direction vector of the global transforms z-axis.
So this basically is the 2D direction vector in the global X/Z plane.
(This will not work if the child is directly looking 90° up/down because the z-vector will then be looking up/down and therefore have a length() of 0 in the global X/Z plane.)
Then the angle to the global "forward" vector is calculated. This could as well be Vector2(0,1) if in your world +z is "forward". If you need degrees then you can use rad2deg.