It is a big jump from young children indiscriminately viewing TV violence without supervision and carefully supervised attendance with your child when you can explain the meaning of any graphic footage. That probably makes all the difference in the world (the child's world).
Still, I personally--through my common sense, my own childhood experiences, and not least because of research by developmental psychologists--would never allow a young child to view graphic footage akin to that which goes on in slaughterhouses, any more than I would approve of watching a film of an execution or torture, even though the latter are also "hard truths."
If you have a different agenda in mind for your child (which is, of course, your call), say, one in which you seem to see her as an activist-in-training, then you are doing the right training for that, if you are showing graphic slaughterhouse scenes, so she will be ready to talk to stangers in a supermarket about their buying habits and the hidden atrocities that occur in slaughterhouses by the tens of millions every day. I'm sure you see your child in totality, not only as a budding activist, but, still, this is something I had not before considered.
I have considered, though, that my own daughter, in her silent modeling of a vegetarian lifestyle, about which all her friends know about her, would be an effective example of a humane way to live. This is not the usual sense of being an activist (which later, of course, she could certainly become more involved), but is one way to live in this world while doing good.
So, two ways to live: by example and by being "activist." I'd say the world needs both kinds. Let's hope we both keep up the good work.