denton: She might be a good candidate for some regular Krav self-defense classes (mine began at age 65, now a spry 68). One of the ladies in my class is just 21.
If your granddaughter had time and interest for such training, it would help her to Instantly react to Any sudden situation (see a bad car wreck, person collapse from heart attack etc),
not just keep her from mentally freezing if a guy assaulted her, and then automatically counter-strike ....as needed.
Even wrist releases from a strong grab (a single wrist or both at the same time "Get in my truck!") are extremely simple, and these are mostly designed for women iirc.