From what was posted on WS during Chris Watts case, CO custody is different than CA. If a parent is awarded full custody of the child,
that parent can move whever they wish without having the consent of the other parent.
I think a parent with full custody, when the other parent has no custodial rights, would be able to move. But since they were co-parenting, if they had never been to court over this to work out a custody agreement and she tried to just move away, he could go to family court and file for shared custody and for her to either come back or leave their daughter in his care as primary residential parent.
So she could not just move away based on the arrangement they had imo. But that doesn’t mean he knew that. I’ve seen parents try to convince the other parent they had no rights etc.