I'm not so sure I'm ready to condemn the passenger just yet. She found a car-pooling arrangement which worked for her, because it meant her husband could have the van during the day, and she compensated the OP with gas money. Since the OP didn't state that the arrangement wasn't working for her, she could only assume it was win-win all around (OP gets help with gas money which she would have had to pay for alone, coworker gets ride to work without having to pull the van into action).
She did say, "Oh it must be inconvenient for you" thereby checking with the OP to see if she was SURE it was OK. The OP seemed not to mind at all. So she continued with the rides, assuming that all was well and the OP was happy not to have to shoulder the gas burden alone.
However, since the OP had secretly been looking forward to this woman's contract ending, and that didn't happen, it's definitely time to put a stop to the rides (personally, I would loathe going 15 minutes out of my way every day, and I would loathe having to chat in the car too). But I'm not so ready to say the coworker has done anything wrong, since she didn't know the OP's feelings on the matter.
How she reacts to being told her rides are ending will be the true test of her character.
I'm with this. I've read countless threads on this forum where posters say, "People can ask for whatever they want. You can say 'no'. They should accept your 'no' gracefully."
I don't think the OP's co-worker is being rude. How can she possibly know that this is an imposition if Gen Xr doesn't tell her? People are different. Maybe if the situation was reversed this wouldn't bother Gen Xr's rider at all to do the same favor.
In a different situation we've got these friends, Jack and Jill, that had their in-laws, Hansel and Gretel, move in with their little kid, Cinderella. For a bit of background Jill and Gretel are sisters and Jack and Jill have no children of their own. It was supposed to be temporary but it ended up being a couple of years because Hansel felt strongly about buying a home and nothing they wanted in a certain location was available. They felt comfortable staying with Jack and Jill because 'family helps out'. Jack and Jill felt the same way, but only temporarily, not for YEARS.
Jack and Jill complained to anyone who would listen how much he hated Hansel, Gretel and Cinderella living with them. He started saying things about their personality, ethics, etc. People were starting to develop a dislike for Hansel by listening to Jack's gossip. When Jack and Jill got around to complaining about this situation to my DH, my DH told him, over and over, "talk to Hansel and Gretel. Complaining to other people is useless and will not resolve the situation. You're starting to hate your BIL and he's actually a nice guy. BEFORE they moved in you should have had an agreement in place about rent, utilities, household responsibilities and a timeline for leaving. But you can STILL discuss these things NOW."
Turns out Jack's major complaint was: "Shouldn't Hansel just KNOW that this is a huge imposition? And not ask? And put me on the spot? Because I'd never ask this of someone else."
Uh no, Hansel's family always helped each other out like this and assumed, when Jack and Jill didn't demur, that moving in with no outdate was fine. So it was up to Jack and Jill to communicate their comfort level of helping out, if indeed they were going to help.
The postscript on this story is not that Jack listened to DH and actually communicated, but that another of Jack's relatives, sick of the complaining, approached Hansel and told him that he needed to get out of there and get in their own place, even if it meant (gasp) 'renting'. Hansel and Gretel, along with little Cinderella peaceably moved out, to this day not completely aware of the hatred Jack was developing for them.
As a side note and irrelevant to this thread, Jack and Jill were pissed when they moved out and got their own place, too. So wethinks Jack and Jill just like to whine and moan.
But my point in bringing it up is: Like OP, Jack was under no obligation to say 'yes' to them moving in (no poverty issues) so neither was OP obligated to be the go-to chauffeur for this woman, he was under no obligation to do it for months or years once he agreed to and could've asked them to leave at any time for no reason whatsoever as could OP.
I think Gen Xr, is like a lot of people that think that other people think the way we do. And they don't. Because they're different. OP would never impose on someone like this, but other people actually do these favors and it doesn't bother them so we HAVE to tell people 'no, I can't/won't do that,' instead of doing it and becoming resentful. Having followed other threads where the OP developed a spine of titanium, I've no doubt Gen Xr will shore up her own and handle this quite well.
And I apologize in advance for frustrating anybody since I'm not the OP. Just wanted to add my two cents.