A mother cat may suddenly become very aggressive towards her kittens for several reasons:
1. Insufficient milk supply from the mother cat: If the mother cat doesn't produce enough milk, the kittens may not be able to suckle properly, causing the mother cat pain. To prevent the kittens from continuing to suckle, the mother cat may exhibit aggression. The solution is to provide the mother cat with sufficient high-protein food, such as boiled chicken breast or canned cat food, to help increase milk production. 
2. Kitten misbehavior: If kittens do things that upset their mother, such as becoming overly dependent on her or disturbing her rest, the mother cat may become aggressive towards them. In this case, the owner should observe the kittens' behavior and provide appropriate correction to help them establish good behavioral habits.
3. Mother cat doesn't accept kittens: Sometimes, a mother cat may not accept her kittens for various reasons, such as the kittens' appearance, smell, or other unusual characteristics. In this case, the owner needs to closely monitor the relationship between the mother cat and kittens and try to create a harmonious environment to help them build a good relationship.
Regardless of the reason, if the mother cat continues to exhibit aggression or restlessness, the owner should seek veterinary advice and help promptly.
