Block her go no contact!! Honestly have no communication with her whatsoever tell your mum to block too it's the the only way.
Block her and don’t let her around you! We’ve blocked my MIL for similar reasons (plus more) and she still tries to mail things and use email but my husband takes care of that so I don’t have to stress with it
Block her. I blocked half off my in laws and haven’t regretted it once
she sounds mentally unwell. any history if mental illness in the family?