OP - If your mother is at-risk of or actually experiencing direct physical abuse, then you need to consider how you could bring her to your home for "a visit,' and then go from there on trying to figure out what she might really want to do away from the abuser and able to have a clearer head on options. If her world has become so closed off by her abuser and she will never leave, then try to encourage her to get out of the house to be around other folks to see if "normality" can help her understand she needs to consider what could be a better life for herself. Along this idea, could she get a part-time job, get involved in a volunteer job, join a gym or community exercise program. If she will not confide in others, then just getting out of the house and being around other folks to build or rebuild social skills and broaden her framework of what is "normal" may be the best way to help her in decision-making.
You might also do some research on resources - local, regional or state - that could provide free and confidential phone line on domestic abuse, programs dealing with and offering domestic abuse shelter, agency dealing with mental health and therapy for low-income folks that may offer a service for your mom. It sounds like the closest thing to a professional she might consider confiding in would be her pastor so suggest that route.