I'm going to not answer a customer and make her wait
Is there that you want to make her wait?
I'm not interested in serving her.
It's your job as a server to serve customers. It's wrong to make someone wait when you are supposed to be attentive to customer's needs.
She will wait in the line, so what's the big deal. I deserve a break sometime.
It's okay to take breaks at work, but there are designated times for such things.  When you are on the clock, it is your responsibility to help customers promptly.  As tired as you may be, just remember that you can rest as soon as the work is taken care of.