Do you know that the girl signed up for this class knowing she would have to dissect a cat? It used to be frogs. No, I can't say I know this for sure, but it makes sense because frog anatomy is quite simple. I've dissected eveything from earthworms, squid, pigeons, rats, to humans. If this course was looking for application to human anatomy, and I'm guessing it probably was, then one needs to dissect something on a higher order. She probably knew, but if she didn't, then I'd cut her some slack.
Perhaps I'm misreading this, but I thought the girl had a problem disecting a cat, not complex animals in general. I know a lot of people with emotional attachments to cats and dogs. This being the case, perhaps the choice of a cat for a high school class might not have been the best of ideas.