Outso Project - Character Design Dev 7 - Rigging

I fully rigged my character using the basic vertex and envelope wrap methods to give my character a bit of life. I did manage to rig each finger, arm, leg, chest, back and certain clothing movements but I came across the common problem where, if she moves her head far back or forward enough, the chin distorts and stretches. I remember being taught how to fix this in year 1 but I forgot what to do. Otherwise it has been my personal best rigged yet.