Here is the sentence you are looking for from Chapter 2.
"The others reproached her sharply, and they went outside."
In this sentence, "her" refers to Mollie, the horse. "They" refers to the other animals. Mollie is being reproached (which means scolded or criticized) because she has been holding ribbons up against herself and enjoying the way they look. This is a bad thing for her to be doing because she is trying to act in a way that the humans want her to act. Now that the revolution is happening, she should be acting more like an animal who does not need people.