I have an employee at the pet store I work at who knows nothing about pets.
How did you know she knows nothing about pets?
I worked with her for 3 months and I've observed her behaviors.
Perhaps she took the job because she loves animals. You should support people who want to do what they enjoy. If you try to teach her, I'm sure she'll be a good employee.
She doesn't deserve that, no excuse for not doing her job. I want to teach her about that.
It's usually easier to train someone than it is to fire them and hire a new person, who might also need training.