X2 - just a little exposure is inevitable with O.C. spray; one of the disadvantages. Insure she knows to clearly understand that prevailing winds will cause overspray onto the user.
The military made me get doused with copious amounts, then go through an obstacle course of training batons vs. punching bags... at Fort Sill, Oklahoma... in the Summer.
Given the choice of being tazed or O.C. sprayed again? I'd take two 5-second rides on the tazer versus being O.C. sprayed vigorously about the face - neck.
Needless to say, O.C. spray IS effective - yet should only serve as a tool to augment her egress and allow for her to gain / distance and separation from a potential scumbag.
Why? One inquires why? Because, AMERICA !!