Is my sister a bad person?

She stole points off a customer's store card to buy candy at her job and got fired. She has a dirtbag boyfriend she keeps going back to. She's mean and beligerant. Sometimes she is very generous with gifts to our family and other times she's stingy. She's never at home, and doesn't participate in family life. Our other sister and I are both honest, straight A students, respectful, obedient, and not ually active, but this sister is nasty. Will she end up in jail? Is there any hope for her? She's 17.