The Breitbart article takes her tweet absolutely at face value and reports it as if it were intended that way.
To me when I read that she is commenting about how society reacts to black shooting victims...
Now, I happen to agree with your interpretation. Most likely she was trying to make this point.
...not anything about the cop.
Probably she was just thinking about the politics surrounding that issue and not the cop himself--but in doing so she dehumanized him. She was talking about a real killing, and a real person, but she casually used his death to make a political point, insinuating things about--again--a real person. If she had written about a hypothetical situation it would be completely different.
She may have been tweeting knowing that her followers were like-minded people who would know how she intended the tweet--but people need to give up the deluded notion that Twitter is like a private conversation in a room with the door shut. It's just not.
I think that article gives far too much information about her and this allows her to become the target of the type of morons who left death threats on her voice mail.
On the other hand, I don't like to see SJWs getting away with smugly spouting the type of bigotry that would get most people fired from their jobs if the targets of their abuse were different (Nicole He springs to mind).
Because there are no consequences for their behavior they feel free to be openly racist, sexist--to indulge in all manner of bigotry--and in this case, to belittle and libel a murder victim soon after his death in order to use him as a political pawn.
I think there should be as much stigma attached to SJW bigotry as any other type of bigotry. Of course, being disgusted at a bigot saying offensive things doesn't justify making death threats against them. I wish the people resorting to abuse and making threats would realize that they are making it harder, not easier, to call out these bigots--but this is the real world. If they had that much sense they wouldn't be doing it in the first place.