I think I solved my problem by looking at the spine plugin source code.
It doesn’t have width, height properties. Instead it has a getBounds() function.
But getBounds() return actual size of the texture, so I have to multiply the size with scale value:
let boyWidth = boy.getBounds().size.x * boy.scaleX;
Little note here is: size.x, not size.width. Because that’s how the spine plugin was written.
Hope this is useful for someone.