Terrified and aggressive cat

Question
I have 3 cats, 1 a neutered male (1 year), 1 neutered female (3 years) and 1 unneutered female (1 year).  All of the cats have always got along without too many problems apart from the older female occasionally hissing and swiping at the younger female.  I would say the older female is the queen of the house.

Anyway, the other night I jumped out of my skin to hear the loudest wailing and screaming upstairs.  When I went up to investigate, the younger female had the biggest dilated pupils i had ever seen, her fur was on end, and she had defacated on the carpet. Something had terrified her. She seemed to calm down over the next couple of hours, but then she suddenly caught sight of the older female and went psycho again. Her pupils went to big that you couldn't see any colour in her eyes at all, her tail was bushy and she was screaming and chasing our other cat in a frenzied attack. The older cat was scared out of her wits.

Another frenzied attack happened the next morning, and the older female again got the brunt of it.  It seems that the boy cat is escaping the attacks altogether and still gets on well with both females.

I got the younger cat checked by a vet who could find nothing physically wrong, but did recommend neutering (she's been in season the last week or so).  Athough, she had been in season many times before and its never caused this kind of behaviour in her.

I've had no choice now but to seperate the two cats.  I haven't got a clue what to do or what started these sudden frenzied attacks. Why is my cat doing this?  She is usually such a sweet little cat who wouldn't harm a fly.  It is so out of character. Will things get better? help!

Answer
Jade,

The vet is correct...get her spayed...right away. That should cure her weird behavior problem. There are times when a cat seems to short-circuit and only the cat knows why it behaves like it does.

Also, a cat that comes into heat more than 3 times without being bred can end up with a serious uterine infection.

Tabbi