Mama cats viviously attacking Older kittens

Question
Mama cat is almost 2, her 3 kittens are almost six months.  She nursed them a LONG time...almost four months.  She was always very loving and tolerant to them.  Now, she acts like they are strangers, or enemies.  If the two boys or one girl kitten come within 3 feet of her, even just walking by, she grows and hisses very loud, then she goes after them, smacking biting, and really attacking.  This is NOT play.  She has become only tolerant of our other two cats, and prefers to be alone.  She says hi to me, and does not mind if I pet her, but she never searches me out anymore.  Has she gone crazy?  BTW, nothing in her food or environment has changed.  thanks!

Answer
Samantha,

There are a number of reasons for your cat's behavior. She has weaned them and is warning them, or she may be in heat are two reasons. Plus cats no longer recognize their kittens as family after they are weaned. That is why there is incest among cats. The kittens may also be in heat. If the kittens have a different smell to them then they are 'new' cats to the mother. Cats recognize smell and not sight. Just like with humans cats recognize voices and not sight.
Is she a calico? That is common with them. I have a calico (fixed) who still growls at her kittens and they are 3 years old!

It would be good to get her fixed and have the vet check her for any kind of uterine infection which could also cause her behavior.

Tabbi