she stopped me before I mentioned the threats he made to kill people and told me that she is a mandated reporter
Your therapist will comply with her mandated reporter obligations, but does not consider herself to be in the business of tricking clients into saying things that will force her to breach confidentiality. You got close to her line, so she reminded you exactly where it was and gave you the option to either cross it and cause a report to law enforcement, or to stop short and talk about things that she can lawfully keep in confidence.
Your therapist will comply with her mandated reporter obligations, but does not consider herself to be in the business of tricking clients into saying things that will force her to breach confidentiality. You got close to her line, so she reminded you exactly where it was and gave you the option to either cross it and cause a report to law enforcement, or to stop short and talk about things that she can lawfully keep in confidence.