What negatives am I unaware of?
There's a word for this (carpetbagging).
Then more broadly there's the question of what a Representative is for. Is it "designated protester for the district"? If so, she's the leading contender. It's my belief that "most effective on-site protester" is not in fact the job of a congressional representative.
It'd be one thing if the choice was between Kat Abu and a staid machine Democrat. But CD9 is naturally progressive, and she's up against Daniel Biss, a progressive with a real track record of getting things done (and unquestioned ties to the district). What I think she's really going to do, best case, is split the progressive vote.
One thing to consider though - while I would normally agree with you on the job description of a congressional rep, there are some moments in history where performative-protest-as-candidate can do more good than ill. I think we're in one of those times, and I'm glad she's able to use the congressional platform to put the executive branch's policies and actions on display.
Think about the message that campaign sends: nobody, in one of the most progressive districts in the country, is as qualified to faithfully represent its progressive ideals as Kat Abu, who has neither ever lived there nor ever held elective office. To me, that's a campaign of contempt for the district.
I've seen the videos of her getting shoved at Broadview. Her immigration politics seem in line with the district. My response to that is: stand on Noyes and Sheridan and throw a rock. You'll hit someone who has identical immigration politics to her.
IL CD9 gets to decide, not me (I'm in CD7). But I do have an opinion!