Karen Uhlenbeck ought to be mentioned. She made deep contributions in the theory of minimal immersions (more generally, harmonic maps), gauge theory of Yang Mills equations (the work of Taubes and Donaldson on four manifolds uses her work), wave maps, integrable systems (e.g. solitons, instantons), etc. She is one of the most important researchers in geometrically and physically motivated partial differential equations of her generation. Although her work as such is probably almost completely inaccessible to any but the most exceptional high school students, the study of soap films and minimal surfaces can be presented to high school students, and some part of her work treats themes that can be seen (in some distant way) as emerging from that source. Maybe something could also be said about solitons, which have applications in telecommunications (although Uhlenbeck's work is not oriented towards applications).
Although her mathematics is not the most accessible, she is a model example of a contemporary woman mathematician of the highest level intellectually and professionally. She has also been active in promoting the participation of women in mathematics.