Brigid's goal seems to be actual pain and injury, so Riley's response is to let out a full throated feline roar before the sound of ripping fabric can be heard.

Fur will be a better barrier against claws and fangs than thin fabric and maybe, just maybe, the sight of a hybrid feline/human will snap her out of whatever rage she's fallen into.

So within a handful of moments, Brigid is no longer fighting an eighteen year old girl. She's now up close and personal with a much larger and fiercer looking monstrosity that lets out another roar, teeth bared as she pushes Brigied away and moves to brace herself on all fours, tail lashing behind her. She's chosen the hybrid form so that she can talk if she needs to. She's not sure that will be an option here.