My cat has been acting aggressive with her kittens. Why is she doing this?

just playing

Yes, she wants them gone. She is done nursing them now. At 3 months old, you should have given the kittens shots, worming and spay/neuter. Call your vet and set up all this now so the kittens are ready to move on to new homes. Spay mom too. If you take them all in to be neutered/spayed, most vets will give you a nice discount.

You can cover the cost of this when you find homes for the kittens.

Yes, it is time to rehome them, she is fed up with them, and get her spayed or more kittens will be on the way!

Nature is telling her to drive them off. She is likely coming in to heat, so wants to get rid of the old litter so she can provide for a new one. Get her spayed, and get the kittens spayed/neutered. Without those hormones affecting her she is more likely be accepting of them. Cats do not have the same concept of "family" that we humans do.

This would be the weaning process. The kittens have become pests and the mother is tired of it.

In the cat world those kittens are grown and she wants them to leave her alone.

She's weaning them.

She's tired of them and it's time for them to leave the 'nest'. 3 months is a long time for a mom to be with her kittens. Start looking for homes for the kittens and then get mama cat spayed.

She could have a mammary infection. Check the address for redness, warmth, or swelling. Otherwise, cage your vet, who is the best authority.

Also, at nearly four months of age they are nearing reproductive age. Unless they are neutered, she will chase them off. Either get 'em neutered, or find homes.

Check with your veterinarian