Now that I think of it, if they're talking about sentimentality, Muffy's the worst character to explore it on.
Let's face it. Arthur's the sentimental one. The episode with Stanley the teddy bear and Pick a Car. Arthur comes from a Middle Middle class family. Not working poor, but not extremely well to do either. Clinging onto something meaningful when you're that young is something a kid is partially necessity when you aren't flooded with toys. Arthur is far from spoiled and manages to have emotional attachments to things. Muffy, on the other hand... subtracting the fact that she'd be rolling in gadgets, she'd be rolling in toys. If you get every single thing there is, there's no real emotional attachment. Maybe it's something you get on a really good day and favor it over something else, but there's not really a huge emotional bond when you get everything. And knowing Muffy, it's all the latest things that she has to have to be trendy. They had an underground complex of all her old toys, meaning she both had a lot of them and grew out of them really fast.
Plus, do they expect anyone to believe any girl at age 8 wants to play with a younger child's elephant plush? I can see someone that age with an emotional attachment at most on a shelf or something. Letting go of the toddler friendly toys at age 8 is somehow treated as an evil brainwashing by computers instead of the rite of passage that it usually is.