GI Bill benefits are a little different for commissioned officers vs enlisted.
Enlisted become eligible for full GI Bill benefits after 36 months of active duty service accrued after 09/11/2001.
Commissioned officers become eligible for full GI Bill benefits after 36 months of active duty accrued after 09/11/2001... however, if the officer was commissioned via service academy (West Point, Annapolis, etc) or ROTC scholarship, the clock for those 36 months does not start until AFTER completion of the minimum service obligation associated with service academy or ROTC scholarship.
So... how would this apply to the person in question in the original post? I believe that the minimum service obligation for Army nursing officers commissioned via ROTC is 8 years (first 4 years must be active duty; remaining 4 years can be completed on active duty, reserve, or National Guard).
So, in order to be eligible for full GI Bill benefits, the nurse in question would need to complete her minimum service obligation of 8 years, PLUS an additional 36 months active duty. This would mean a total of 11 years of service, at least 7 years of which were on active duty.