Originally Posted by
Reddish Mage
I think you are greatly misremembering how the episodes play out.
In "The Spear of Selene" its Webby, not Dewey, that decides to go after the mysetery of Dewey's mom.
In "Terror of the Terrafirmians" its Webby and Lena leading Huey on an adventure he is reluctant to go on, with Webby constantly making the point that the terrafirmians are real.
Moreover, in "From the Confidential Casefiles of Agent 22" Webby doesn't just tag along. She sneaks her way in, while Scrooge goes after her aunt.
The earliest episode "Woo-oo!" has Webby is the one who approaches the boys and shows the boys her research on Scrooge and then Scrooge's artifact to impress them. Then they mess things up playing with the artifacts. She's not tagging along, they are entering her world at her invitation, then proceed to make a mess.
Webby initiates making friendship braclets with Lena in "Jaw$" as well as their involvement with the shark because that's what Webby wants to do.
Webby doesn't have her "own" desires only in the sense that much of what she wants is to understand and experience Scrooge's manor, his myseteries, adventures, and his artifacts. In many ways the triplets are exactly alike in this respect. However, Webby, unlike the triplets, doesn't have expectations on Scrooge's stuff, so in this way she's an outsider. That doesn't stop her from having more involvement with all the cool stuff going on than anybody, its only more conceptual then physical. She's doing exactly what she wants to.