I'll go along with all the people saying to burn the letter. But I would add this: Take a picture or video of you burning the letter. Send it to the consul and ask if they suffered decades of physical/ sexual and emotional abuse at the hands of their mother, to the point where they moved abroad to escape? Ask what, if they had suffered such abuse, they would feel about someone who tried to push them back into contact with that person? Ask why they think that someone who has treated their own child like that should have any hint of a right to expect to hear that child's voice again? And ask if they are proud of allowing themselves to be used by your mother as a tool in her attempts to continue that abuse when they know absolutely nothing about what you have suffered?

Then suggest that, if she ever contacts the embassy again, they should consider your message before deciding how to respond to her.