Now, I will freely admit that Brianna being attacked by the buffalo was a brief part of a brief scene in an episode overall devoted to Jamie’s near-death and his bonding with Roger, and it was actually a great scene for Bree, short as it was.
When a buffalo (which Jamie had managed to wound before being bit by a snake) showed up at the Ridge and was getting ready to charge a terrified Lizzie and a bawling Jemmy, Bree heroically raced into action, grabbed the animal’s attention, and got it to chase her rather than possibly trample and kill her young son.