Who is liable if my pet hurts my roommates infant if my roommate is (knowingly) increasing the level of danger?

I have pet rats. I have had these rats for a few years now. About five months ago, my friend asked if she and her young baby could move in with me because her living situation was stressful and potentially dangerous. When she asked, she knew that I had pet rats and what kind of cage I kept the rats in. I keep my... show more I have pet rats. I have had these rats for a few years now. About five months ago, my friend asked if she and her young baby could move in with me because her living situation was stressful and potentially dangerous. When she asked, she knew that I had pet rats and what kind of cage I kept the rats in. I keep my rats in a feisty ferret cage (Image here: http://www.petworldshop.com/pictures/feisty-ferret-home.jpg) which an infant could easily get their fingers into. I had also informed her before we moved in that the rats most likely will bite anything stuck between the bars of the cage, assuming that it's food.
When we moved in together, I constructed a "rat barrier" around the rat cage. A few months later, she took it down, saying that it was "ugly". Now that the baby knows how to crawl, all that he wants to do is put his fingers in the rat cage. We put the barrier back up, but she actually deconstructed it after about a week and threw part of it away.
I have told her now that she needs to buy baby gates that she can tolerate in order to ensure her infants safety. She has yet to order any baby gates and it does not seem likely that she is about to. Her baby is a fast crawler and she is constantly leaving him alone in the same room as the cages for periods of more than a minute (way more than enough time for him to get his fingers in the cage).
Note: My rats do not have bad temperaments, they just tend to assume that anything stuck between the bars of their cage is food.

So here are my qeustions:
1. If one of my rats bites her infant, am I legally liable? I feel that I have done enough on my end to protect her infant and that she has not done enough on her end.
2. Also, she has advised me that she would hurt or kill my rats if they did any damage to her infant. Would I be able to pursue her legally, considering that I have done plenty to inform her of the dangers they would impose, that she knew the danger that they imposed beforehand, and that I have attempted to protect her infant from possible danger and that she removed those precautions?
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