She means that Bennie isn't able to live on his own yet; he's only ten and can't live without proper guidance. His grandmother is the one who takes care of him. Since she's going to die, he's going to need oversight and guidance from a different person to make sure that he grows up happy and healthy.
Grannie is trying to make plans to ensure that everyone in her family is taken care of before she passes away. For example, she wants to make sure that her daughter marries Joe so that she will have a good life. She tries to take care of all the problems herself, even suffering through the knowledge of her impending death alone. However, before she dies, she finds out that Bennie knows the truth and has been working to make her life easier.
Miss May, Grannie's friend, was going to take care of Bennie. However, she died before Grannie and that meant that Grannie needed to make alternate plans. She's a woman who believes that she can help guide her family through life even after she's gone. Part of this includes making sure arrangements are made for her family.