She was drinking wine in Boston which presumably puts her age over 21. Given the BS fast track and amazingly smartness people in Trek are gifted with, this would likely put her as a Postdoc level or professor level which, without knowing any more could be the same level as the sister, who may have chose to go into some professional role right right after finishing grad school. The enrolling line kind of muddles it. Maybe it's sloppy writing. Kind of like the horrendous sloppy writing on the CW where people stupidly get multiple Ph.D.s instead of just working on projects in new areas as a degreed scientist.