My eldest is also going through this...she is 19 now and was 17 when DH died. They had a volatile relationship and he died so quickly after his diagnosis, that there was little chance for closure. DH was her stepfather; her father died when she was just a baby.
She has zero motivation and she drags her feet when it comes to anything resembling adult responsibility. She won't study to pass the test to get a learner's permit, she won't submit any job applications, she dropped out of school and now she won't do anything to earn her GED. She refuses to go to any sort of counseling, grief or otherwise. When I press the issue, it generally degrades into a fight with her threatening to live on the street and become a stripper. Last time she threatened, I told her to go....she backed down later that night.
I have no advice for you, as I am apparently failing miserably in a similar boat. But you aren't alone. Hugs.