Use desensitization and counter conditioning to help her feel better about strangers approaching. Plus don't let strangers stick their hands out at her or bend over her or look her directly in the face.
The link below has more details about dogs who react to other dogs. Just replace "other dogs" with other humans.
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Please don’t listen to any advice that is just a repeat of television shows. TV is for entertainment and ratings – not education. So please do not listen to advice about alpha rolling, dominance, pack leader, showing who’s boss etc..
There is a reason why the screen on those TV shows flashes “Do not try this at home” – because the techniques are extremely unsafe.
Please absolutely no alpha rolling, leash yanking, hanings, no leash corrections (same as yanking, jerking). There are better ways to treat your best friend. Please no shock collars
If someone says it doesn’t hurt, it probably does: http://blog.mysanantonio.com/latrenda/2011/05/when-someone-says-its-doesnt-hurt-it-probably-does/
ETA
Please do not kick (tap)
or yank (pull on the leash)
This will make your dog feel worse about other people, not better