Though, did she knew the background of the dogs? And if so, cause she should, wondering why she choose to walk in there with a cane. Maybe she just forgot and did not thought the dog(s) would attack.
I don't know if she specifically knew the dog had been beaten with a stick and, even if she did know, probably wasn't enoough of an animal psychologist to make the leap that a walking stick could trigger that past trauma.
It is, of course, only a theory that the walking stick is the reason for the attack. They couldn't ask the dogs or read their minds. But given the past hitory of the alpha-dog and the timing of the attack it does seem pretty likely.