Momma Cat Biting Kitten When They Try To Nurse?

My momma cat bites my babies when they try to nurse. She does this because she doesn’t want them near her litter box, and they are just too little to understand that they have no choice but to obey her commands! I’m trying my best, as a nursing mom myself, not to hurt them even though it’s so hard with the teeth…it’s really embarrassing for me as well. How can i show her that i am more confident now? I know what she is doing is wrong and cruel…I do NOT think its normal behavior from an adult cat or mother for that matter. Any advice??