JOEL - The Church will never encourage someone to leave the church because of lack of support from family. This would be a decision the person would have to make on their own. This is a problem that she should have dealt with before she became a member. If the problem of her family disowning her was more than she could bear then she could have perhaps waited a while for a better time to be baptized. Hundreds of new converts face this type of delima every year. My own wife's parents felt the same way when she became a member. But they did not feel that way for long, especially when grandchildren started coming on the scene :-)
Hopefully, fellow church members will give your sister enough support and encouragement that will help her get through her beginning days as a new member. She should continually try to express her love for her family and let them know that she has not disowned them. Time will often heal the wounds and they will eventually be able to tolerate and accept her decision of being a member of the church; especially when they see how much happier she is and how much better her life is as a member.