D.va is just smart. She knows that the devs will do the opposite of what you ask them. Which is why she says “nerf this!”. She knows how to use reverse psychology 
Also, I’ve heard somebody speculate that they probably didn’t want to nerf D.va because the devs want to make D.va + Juno synergy work. Juno can’t really be buffed without upsetting the playerbase, so I guess they just kept D.va as it is in the hopes of the synergy becoming meta.