It sounds if your mother lives alone and possibly doesnt have a wide social circle and that her contacts with other people, apart from you and your family, are people at work. She is now faced with retirement and the end of her social interaction with work colleagues and now you to plan to move away.
If my suppositions are right stand in her shoes briefly and see the world from her perspective. She is probably absolutely terrified of the major change that is coming into her life through retirement and the loss of the social interaction at work and now you too are leaving. She will be living alone with little contact with other people and she lacks the skills or confidence to move out of the little world she inhabits.
Is there anything you can do to gently encourage her to step outwards into a wider life? I have no idea what she is like or what she enjoys but could you accompany her into looking at life outside her home, attending WI or Townswomens Guild meetings, working in a Charity shop or doing other voluntary work, joining a pensioners club or taking up a sport like bowling. I specifically suggest you accompany her at the start because people like she sounds to be like would never have the confidence to go anywhere new by themselves. You obviously have the personality and confidence to take new intiatives and spread your wings, but not everybody does and your mother doesnt seem to be among them. The best thing you can do is help your mother reduce her dependence on you and step into a wider world and enjoy retirement.