Welcome to HCM,
Nose bleeding is called Epistaxis
,at her age 73 years,high blood pressure
is one of the many possible cause.
Please recheck the her blood pressure and it is more than 160/90 mm of hg she should take anti hypertensive therapy and reduction of salt in diet.
Please also check for bolld test like Bleeding time
,clotting time and prothrombine time with blood count and platelet count
There are some local causes also hence vist a ENT Surgeon to see any bleeding point if any it can be treated locally by surgery or alternately.