It seems that an animal companion, summoned creatures and/or animals dominated with AE do nothing about hostile animals. They just stand still, and the "attack nearest" command does nothing. Similarly, hostile animals seem to ignore such summoned/dominated helpers and instead go straight for the PC.
My druid PC recently died to an attacking desert lion (oh the irony), which I thought I could repulse with the help of my own animals, including a dominated lioness. None of the three helpers would do anything, which I realised slightly too late.
Makes you wonder, by the way, why e.g. Tribal Shamans can avoid animal attacks altogether, whereas druids and rangers must hope for their Animal Empathy modifier to be high enough... but that's another matter.