If your roomate's cat ruined your coach, then legally, she is liable for them--fixing or replacing. It also sounds like you have the evidence to prove it. However, before suing, (1) ask yourself if the amount you'd win is worth the damage to you relationship with your roomate (people usually don't stay roomates or friends after a lawsuit) and (2) whether economically it's worth the cost.If the answer to (1) is "yes," then probably you would need to consider bringing a claim yourself (no attorney), ideally in small claims court if you have it in your area; it's almost impossible to imagine that even the cost of replacing the coaches would justify (2) the economic cost of a lawyer and lawsuit.