OMG she vapes in your car?
There are folk whose cars I vape in, those who have expressly said I can. I wouldn't even ask, they've offered, knowing I vape, and even then... windows down, minimal vaping and if its too cold for windows down, I wait!
The hanging around after work is a pisstake but its also a great get out: 'I have to leave bang on time each day, there is no leeway in my schedule so you're welcome to a lift but if you're not standing by my car when I get in it, I will have to leave you behind'.
Don't tell her a time, don't tell her you'll let her know when you're leaving either, onus is on her to be at the car, to find you etc.
Then stick to it, if she's not at your car when you get to it, get in and piss off home!
And after that one has sunk in you can add: 'Child has new after school activities some nights so I may be unavailable for lifts'.
Thats if you really feel you can't just say No!