Hi
I would suggest looking into how to handle the suicide threats that involves outside resources that are trained to deal with such threats. Us everyday are not skilled enough if you ask me and its serious situation when it happens.
Do it before you reach "intervention point". She will feel threatened and overwhelmed and try which ever action she feels works best to gain control again.
If she reaches a point and mentions suicide, your next calm step is to dial the number of the professional and take plan from there. The plan you, husband and professional put in place for that moment. If she doesn't then great! One step in right direction.