I am sorry about this last turn of events. I am happy that the drug company is willing to shoulder some of the costs; they really didn't have to do that. And I honestly hope you are not considering any legal action. They may have actually been party to causing harm, but that was not their intention. I rely on big pharma for some drugs that really make my life a lot less painful; and even though some side effects are expected, I know that I am willing to go through them and to take the chance of a negative reaction in exchange for the benefits. Someone shouldn't be punished for offering me this option. And they probably shouldn't be punished for offering you and Latte that option. At the same time, I feel for you and for the decisions you and your vet have made for your cat. It sounds like everyone here has Latte's best interests in mind.
The best to you.