Honestly your only option is to stop giving your Mom power over you. Only talk to her when you feel up to it, block her number if she spams up your phone, and call security if she shows up at work.
There is no way to regain control without some form of struggle, but you can't get what you want without regaining control. This may indeed require treating your Mom like a stalker, because that is in fact what she is. Her power comes from her having groomed you to be afraid of the consequences of denying her, only you can put an end to it.