The daughter managed to convince a social worker that it was in her best interest to be put into foster care. It isn't up to the child to decide, there must have been a reason.

In cases where substitute care for a minor child becomes involved (such as a group home, foster care, or another type of institution) both parents may have been ordered to pay child support.

Your fiance should have been aware of this.

http://www.supportcollectors.com/csrc/wisconsin.php