Why Is My Cat Growling At My New Kitten?

My cat is a 8 year old female with two kittens. She was introduced to the kittens when they were 5 weeks old. Now she is growling at them and starting to attack them by biting at their necks or tails, scratching at their ears/eyes, etc. The kittens are barely 3 months old but very healthy – no sign of infection that I can see (unless I am not seeing it). Do you think this behavior will escalate as they get older if my cats has any intention of killing them? Or do you think I should just let her be? What would you do in this situation? Why does my cat act like this towards the new kitten now after having happily accepted him into our home for 2 years even though he is only 3 months old? Thank you!