$600 is not nearly enough to support a child.
Hypothetically, if it was just one adult and one child living in a two bedroom home with $800/mo rent, $150/mo electric bill, and $50/mo internet (a necessity for a middle-schooler these days), it would be fair to say the child's portion was 50%, which would leave only $100 for her food for the month.
It is different when the custodial adult is one of the parents because the parent has a natural obligation to provide support. A grandparent does not have a natural obligation to provide support and if one of the parents isn't paying their share, the other parent must.
I hope that your dh is stepping up and paying for anything extra his dd needs in addition to the child support.
If there is already an existing court order allowing visitation, get a lawyer and file a motion for contempt. If the visitation is not already in writing, get a lawyer and make it so. It does sound like at this time the child should be living with her dad, even if that needs to be accomplished gradually. Best wishes in making that happen!