I'm thankful you are concerned about your mother; I receive far too many letters from elderly people who feel abandoned by their families. The Bible says, "Religion that God our Father accepts as pure and faultless is this: to look after orphans and widows in their distress" (James 1:27).
My first suggestion would be to share your concern with your mother's doctor. Her doctor probably knows her situation better than you do, and can help you decide what is best for her. In fact, unless her doctor is convinced she is able to live safely on her own, she may not be allowed to leave the rehabilitation facility until some other arrangement is made.
Then look carefully at the options. Can someone be employed to help her if she returns to her apartment? Or could she move into an assisted living facility, at least until she regains her strength? Down inside, she wants to keep her independence (and you need to respect that), so if possible, find some arrangement that allows her some independence.
In addition, ask God to help you be sensitive to your mother and her feelings. This is a hard time of life for her, and she needs to know you love her and want what's best for her. Most of all, remind her of God's constant love for her a love so great His Son was willing to give His life for her eternal salvation.