If you do want to tell you that the friendship is over with, but do not know want to learn how she would act when she hears it, then the appropriate thing is to send her an email with a brief statement and then put her email address on ignore (auto-archive, auto-delete, or whatever your email client offers). And put her phone number on "forward to VM without ringing", and, delete her VM's without listening to them.

That should take care of your issue.