"I wanted the summer model" oof, I'm not rly a luxury bag person but other than high end society events I doubt ppl would notice versus the sales women convincing him to get an "upgrade"
My assumption is, like most consumers of high-end fashion, her goal is to flaunt how rich, happy and loved she is by showing off that she owns the latest brands.
She wants to give off image of being a wealthy celeb whose husband is able to casually drop a significant amount of money on a new bag by posting about it on social media or showing it off to her other rich friends.
Since the bag is no longer the latest model, it's no longer useful for projecting that image. Her friends or followers will inevitably ask
"Isn't that last seasons bag? Why didn't you buy the latest one? Can you not afford it? Did you buy your bag second hand or something lol?".
It's irrational but that's the way people like this operate.