How to gain my chinchillas trust again?

Our chinchilla has finally warmed up to us. Then my grandmothers cat showed up and was standing near her play pen. When my boyfriend shooed the cat off and tried to take her out the pen, she bit him and lost clumps of hair. We got her in her cage, but now she wont let us near her. She backs off and acts as if she is going to attack. What can we do to gain her trust back? I am concerned that she is permanently scared because of that darn cat.