I feel like I should tell off my roommate for not feeding the cats
Is feeding the cats her responsibilty?
I don't like cats but feeding them is part of the lease agreement and she agreed to be the one that does it.
Your roommate was irresponsible in not doing what she promised. You might want to try have a more civil discussion instead of just going off on her.
Nah I'm going to have a big fight with her.
You really need to hold off on starting a big fight. She'll be more likely to work with you on the problem if she doesn't feel like you're attacking her. After all you really just want her to take care of feeding the cats like she said right?