Assuming CA relinquishes jurisdiction and AZ then possesses the ability to modify the order, there is now a presumption for joint custody in arizona absent evidence to the contrary. See A.R.S. 25-103. Examples of items that would rebut a finding of joint custody are domestic violence, substance abuse, child abuse/neglect, mental concerns, etc. This is not meant to be an exaustive list, but provide you a bit of insight as to the items I am sure her lawyer will attack in attempt to rebut the joint custody presumption. If there are no findings substantiated, the court should be inclined to award joint custody moving forward.