Cats got along for 4 months then 1 snapped

I have to female cats 1 is about 7 years out the other 1 is about 1 year old (may be pregnant). When we got the youngest cat the oldest one didn't like that 2 much but in a few weeks time they got along they didn't hiss or growl at each other they would play fight and chase each other. Now the other day i was going to feed them and the oldest cat snapped and attacked the youngest one. I mean there was fur flying and moews and hisses it was bad. So I separated them untill they both calmed down. Now when the oldest cat seen the youngest cat again she pounced of the chair and charged right at the youngest one with a weird look on her face. So the reason i am writing this is i was wondering if anyone can tell me why the oldest cat just snapped and went crazy.

Is the older cat spayed? It may seem OK to have 2 unspayed females because they can't breed with eachother, but it can actually result in disputing between them. If they neither is spayed they are fighting for breeding rights. A second thought I have is if the 1 year old is infact pregnant is it possible that her smell has changed? (I don't know just throwing it out there for others who know more about pregnant cats) If her smell has changed your other cat may not recognize her as her friend. I recommend that unless you are a breeder they should both be spayed, it's actually much healthier for them.

Originally Posted by Rang_27

A second thought I have is if the 1 year old is infact pregnant is it possible that her smell has changed?

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If your younger cat is pregnant she will certainly smell different to your other cat so that could be the reason.

I agree 100% that these cats need to be spayed, if they are getting outside they will get pregnant time and time again. Also if one is pregnant it will smell different as has already been said.
Another option is that the younger cat is sick. I advise a vet trip ASAP. When a cat is sick its friends can turn on it. I don't know the exact reason, I'm sure somebody will advise you why but get the younger cat to the vet ASAP to prevent this happening again.
Good luck and keep us updated.

thank you for your help. I am making an appointment to the vet today. I hope everything goes good. I will keep everyone informed