You are Disney, a few thousand people on Twitter can't hurt you in any significant way and there are probably waaayyy more fans who like her character and think firing her for tweets is stupid.
Yes, but you are also Disney, named after Walt Disney, a man of Jewish descent, and your current CEO is of Jewish descent, so probably disparaging the Shoa is not a good career move. You are also Disney, a corporation that has a very specific corporate culture and image, and part of the deal that includes paying you mega Disney bucks is to act like Disney wants you to act.