She bought herself a new car back when he was gambling but before he confessed to her, and he was very graceless about her having done so.
And then, back in April 2006, we got
"Shula tells [Caroline] about Alistair’s outburst over the car, and how Daniel caught the full force of it. She can’t take Alistair’s mood swings, but blames herself; she should have seen it coming, and now there’s nothing left between them. And even worse, she’s depriving Daniel of a father for the second time. "
In other words, it’s not as if this were a new disillusionment with him.