B.C.
Out of control type temper tantrums past 3 yrs old are not normal.
You've been having issues with her for several years now and things are getting worse.
First - completely clean out the car - no toys, chips, candy, snacks, projectiles of any sort - zip zilch nada.
You've got to understand how dangerous that is - if you crashed you could have killed yourself, your kids and who ever else you crashed into.
Honestly if I were in that situation I would have pulled over and there would have been hell to pay right then and there.
Second - talk to her pediatrician and get a referral for a behavioral/psychiatric evaluation. You need the tools to learn how to deal with her and if meds are recommended then think them over seriously - living an out of control life isn't going to help her make friends and it won't be doing her any favors.
Third - privileges are constantly earned through good behavior - if she didn't earn them then no tv/computer/video games - find her currency (what ever matters most to her).
Fourth - give the other kids time/breaks away from her - you don't want them picking up any bad habits plus it's a strain being with someone who's tantruming a lot - does she throw things at them or kick them?
You have to protect your other kids.
Maybe they can go visit grandparents or your oldest can visit them on her own for a bit - the kids don't always have to go everywhere together.