I  am a lawyer in CT and practice in this area of the law. Defamation is actionable if the defendant makes a false statement of fact that they knew or should have known was false to another person and injures the person's reputation.  The issue in this case is whether your ex truly believed that you were suicidal.  if she has reason to believe you were on drugs, then the her inference that you were suicidal is not completely unbelievable where a jury would find that she made this statement knowing it was false.  I suggest that you not pursue this matter and assure her that you are not suicial.