Have Cat Questions? Ask a Cat Vet Online.
Any time that you have sudden agression or behavior changes, you need to see the vet to rule out a medical cause.
Occasionally, you will see a struggle between the females for the "alpha" or the strongest position. This should ease within a few days if that is what it is.
If it doesn't, you need to see the vet to rule out a medical reason for the behavior.
Let me know if you still have questions.