Health insurance question and Diabetic child in college.Can he be covered.?

step mother took diabetic step son off her family plan out of spite.His real mom is dead.He is currently on medicaid but it will stop when he turns 19.He is in college full time.He does not stay at her home.Her real daughter is on the plan and so is his dad.The other daughter will be leaving for college in August and she won't be living at home.The diabetic had to go to a comm college cause his dad and step mom never saved for his college.Step mom says she can't keep him on the policy cause he doesn't live at home.but he is in college full time.Is she lying does anyone know.She has always hated him and dad won't leave her cause she is his gravy train.How can it be different for one child who goes away and one who stays in town.