My mum used to send mw to and from my hobby from 8 years old in a taxi on my own! I was fine however it was way too young to be on my own with a stranger in a car! And i woukdnt do that to my kids at that age. She just wanted me out of her way! But at 12 it will be fine!
My DD age 12 years always gets a taxi home from swimming once a week. I just watch out for the cab and then run out to pay, mainly because if I gave her the £15 there is a strong possibility of her losing it during her school day!