Poor you, Driven! I really feel for you. I have had two different experiences of giving endless lifts to a fairly nearby-living colleague. It would be perfectly fine, IF they managed to get into their heads that it is a "favour" and not a duty. They don't have a car, so they have no expenses, no road tax, no insurance to pay, no MOT, etc. etc. but given my experiences, I would now just say NO straight away.
I started giving a lift to a colleague (who asked) - and as she lived quite close, I saw absolutely no problem, and was pleased to be able to help. However, after very many mornings sat outside her house waiting for her... (she was always late, except for the very first lift) I started to have my mis-givings. Then, on the way home, it began ... "could we just stop at xxx convenience store, just want to grab some milk" - then, "could we just take a slight detour, need to drop a birthday card into someone's house" ... (just two that I remember out of literally dozens of such requests) over a 6 month period which lead to me feeling like her personal courier. It came to a head one night, when I particularly wanted to get home promptly - and again it was "I have no loo - rolls, please can we just stop for two minutes at xxxx convenienc e store?" "Please" .. So I did. Ages seemed to go past, and in a high degree of irritation, I got out and went into the store. She was leaning over a TROLLEY, with what looked like about 15 different items, having a lovely chummy chat with a friend!!
I returned immediately to my car and drove off - leaving her there with her "friend" and her shopping! After a very unpleasant text messaging session, she finally got the message. But it was very unpleasant an unnecessary. Another time, (previously) when I had agreed to give another colleague a lift ( a man) I became very unsettled, as whenever he got into my car, early in the morning, he STANK of alcohol, such that I had to roll the window down even if it was freezing cold, as the smell was making me sick. For these reasons, I now believe it is best to just say "NO" - always. And never again! Please don't feel bad, you did her a lot of favours, and I would really, really recommend speaking to your managers, and telling them how stressed she was making you with her demands and her spiteful gossiping about you (Usually a big no no in a big company!) which is why you made a mistake on that particular evening. Good luck, but please, seriously, do think about explaining your side of the stressful situation to your managers? xx