I would send her an email telling her you do not want to talk to her any more. That it upsets your wife and that it the last thing you want to do. Also that she has spoken badly about your wife which hurt and upset you, so from now on you wish to have no more to do with her.

Then delete your account.

After two years of upsetting your wife by talking to her I feel that it would make your wife feel better if she knew you had defended her to this woman.