Based on what I've heard and seen of her behavior in the show, she definitely does come off more as a Hate Sink than The Scrappy. For those not familiar with the character, her actions include things such as the following:
- Blackmailing her older brother Arthur into helping her look for her blanket and causing him to miss a movie marathon with his best friend as a result.
- Making an insensitive comment about getting a "good dog" at Arthur's expense when his dog Pal was sick.
- Preventing Arthur from watching a show he wanted to see on TV simply out of spite at her own favorite TV show being cancelled.
- Manipulating Arthur into taking her to a science museum against his will (and scamming her friends out of their money in the process!).
- Breaking a model airplane Arthur worked on for weeks without remorse.
- Using Arthur as a meat shield from a splash of water (even saying that an older brother can be used for an umbrella!).
- Purposely trying to make Arthur feel bad about things he missed out on doing during the summer.
- Trying to convince her and Arthur's parents to make Arthur move out of their house several times.
- Often making rude and condescending remarks at his expense.
- Often having Arthur or her friends take the blame for her behavior.
- Getting Arthur humiliated in front of her preschool class and his friends by having him act like a chimpanzee.
- And many, many more very clearly and objectively unsympathetic actions like that.
Those actions certainly would seem to indicate she's a HS, since if the writers wrote her to be this this blatantly horrible and unlikeable while still expecting the audience to sympathize with her, they would frankly have to be either mentally retarded or out of their minds. But on the other hand, I am not entirely sure she is a HS, due to the fact that she does have more likeable moments on occasion (such as in the episodes "D.W. Thinks Big", "Arthur's Knee", and "Grandpa Dave's Old Country Farm"), and redeeming qualities such as genuinely caring about her friends, parents, baby sister and grandparents, but those are few and far between and her sympathetic portrayal in "Arthur's Knee" one may seem like an Out-of-Character Moment that is done for plot convenience, plus the aforementioned redeeming qualities seem to be de-emphatized by the narrative in favor of what a massive pain she is to Arthur. There's also the fact that she's listed under Unintentionally Unsympathetic on the Arthur and Western Animation YMMV pages for two specific episodes ("Arthur's Big Hit" and "D.W.'s Very Bad Mood", which is mutually exclusive with HS for obvious reasons. That being said, I'm not sure her lack of sympathy in "Arthur's Big Hit" is actually unintentional, since again, her behavior therein is so blatantly unsympathetic that it's hard to believe it's not intended, but she's definitely meant to be sympathetic in "D.W.'s Very Bad Mood". There are also episodes where she is the focus character, meaning the audience is clearly meant to be on her side in those episodes. Is it possible for a character to vary between being a HS and not depending on the episode?
It should also be noted that Marc Brown, one of the show's producers, recently said in an interview that D.W. is "triply lethal" based on the fact that she's based on his own three sisters he had growing up and hoped that kids watching the show wouldn't imitate her trick of dressing up as Arthur in "D.W. the Copycat", so it seems even he views the character in a fairly negative light.
So what do you think? Should we move her to Hate Sink or keep her on The Scrappy? Or perhaps move her to Base Breaker instead?