"The cat is hungry. She eats meat."
Translation:Die Katze hat Hunger. Sie isst Fleisch.
There are no official rules for the usage of German words, so there is no wrong and right, there is just usual and unusual. I'm sure there are some Germans using essen for animals for various reasons, but I'm pretty sure it's a minority. I'm a native speaker and I can't remember anyone who's doing it, so my advice can only be: learn to distinguish between the two.
Yes, but in this case it's not the gender that the pronoun need to follow, it's the species. We went from a proper noun of 'cat' to it's pronoun of 'she', but we're still talking about an animal eating. And, that should be 'frisst'.
The ONLY thing I can think is that 'frisst' or 'fressen' is only applied in a sentence with a proper noun of an animal (Cat, dog, cow, duck...). But, not for a sentence with only pronouns as a reference. (as chinmaypat13 suggested)
The ONLY OTHER thing I can think of is that Duolingo has this incorrect and it should be frisst instead of isst.
Also, if I simply said, "Sie frisst" (she eats), "Sie frisst heu" (she eats hay) you'd immediately know I was talking about an animal, not a person. If you pointed to your cat eating, you might say, "Sie/Er frisst." AH! But I do remember that you can use essen & fressen for animals, but only essen for humans. Although, that does not explain why 'frisst' is incorrect for the pronoun of a cat.
I had to rephrase my comment a bit, as I was a bit irritated by the style of your comment...
I can just tell you that the question of which verb to take is not related to the use of a pronoun vs. a noun. The only reasonable explanation is that Duo sometimes uses essen for animals, which I find arguable as a native speaker.
The only alternative is that "sie" refers to a woman to which the speaker is pointing, but that was actually just a joke from my side, as it's more than unlikely to find something mean like that in a language course.
No, actually that doesn't matter. One versions is as correct or incorrect as the other with essen. You can always play this game with pointing to something or someone else with a pronoun, but in a normal conversation you would never do that, and if, you would make your point clear by gestures or articulation. In the current form we have anyway to assume that sie refers to the cat, with a compound sentence or two simple ones.