My joint child has Medical Assistance in Minnesota. Her mother chose to take her to a dentist that does not accept her insurance, without notifying me that she went to this appointment; I have joint legal custody. Prior to this, I sent her information about dentists in the area that accept her insurance. She still took her to a dentist that did not accept her insurance without me knowing about it, I then received a bill for half of that appointment, am I legally responsible to pay that?