Not really. You can list who you would like but the decision is up to the court. And it's based on the best interest of the child. What you put in your will only tells the court who, at the time you signed your will, you felt it would be in your child's best interest to reside with.
As long as the court agrees, the person named agrees, there are no circumstances that could make that person not the best choice, and there's no battle between relatives, the person listed will be very likely to be the one appointed but a will simply states the parent's desires. It assists the court but is not binding on the court. The court appoints a guardian. Not the parents.
That being said in cases similar to this a child is often released by LE or a hospital to next of kin or whatever kin is able to take the child. At this point ALL her family have been heavily investigated/vetted by LE.
So social services would be likely to authorize release to family pending a legal determination as to temporary and permanent care.
