I guess you could use the system is between angles condition..
I would use the body angle to compare with, in this case..
so that would be something like this:
angle(head.x,head.y,mouse.x,mouse.y is between body.angle-45 ; body.angle+45
head rotate 1 degrees towards angle(head.x,head.y,mouse.x,mouse.y
head rotate 1 degrees towards body.angle