Your stepmom is probably going to prematurely unalive that cat unfortunately. Cats don’t generally understand how to drink water from a bowl because it’s not normal for them as they typically get all of their water from the blood of prey they kill. If she’s not putting any water down specifically for the cat and only feeding dry food, you can guarantee the cat is going to become dehydrated.
After that it’s only a matter of time until other complications develop: https://cats.com/dehydration-in-cats
Source?