sisters acting up

I have two cats that are sisters. I was wondering if anyone can help me with a question. They used to sleep together as kittens and as they grew older they started being more independent of course- they are now 4 yrs old. Although they never sleep together anymore they do tend to always end up in the same room as each -they kind of follow each other around.
The thing is they get touchy when they are right near each other. They will pounce, swat, and occasionally hiss at each other. Sometimes the smaller one seems to be afraid to pass by her sister. They never draw blood and rarely get into full out fights, but just seem well, like they really don't like each other.
Another worry is that i feed them together but lately it seems like the little one won't eat her dry food until her sister leaves. I guess they are fighting over who is the alpha cat, but i was wondering if I should be worried or if there is something I can/should do for them not to be so touchy. Any advise would be helpful, thanks.

My first question: Are they spayed?

Assuming that they are spayed, you could try plugging in a couple of Feliway diffusers throughout the house, particularly in the cats' favorite rooms. The diffusers emit a synthetic pheromone that, for many cats, seems to have a calming effect, such as what they get when they mark objects with their facial scent glands. The emissions cannot be detected by humans. You could also/instead try putting a couple of drops of Bach's Rescue Remedy into their water bowls, or have them lick a drop or two off of your finger, or rub it onto one of their front paws. Rescue Remedy can also calm cats down.

These are the simplest approaches.

I'm also curious as to how long this has been going on, and when the smaller cat's last vet visit was. Sometimes cats who are ill get attacked by other cats who sense weakness. But truthfully it doesn't really sound like that's quite what's going on here.

At feeding time, could you feed one of them in a separate room, at least temporarily?

I'm sure other members will chime in with more ideas.

Thank you for your prompt reply.

Yes they are both spayed and both have had a vet visit last month. The smaller one, Suki, has always been more hesitant but that doesn't stop her from acting out on her sister, Himiko, sometimes. I may try feeding them separatly again but Himiko (who is on a diet since her last vet visit she was at 15lbs!!!) gets very jealous and just waits by doors to get to the food in the other room.

They have acted this way for awhile-maybe a yr or so now, so although lessoning the snacks and food may have made Himiko perturbed i don't think this is the reason for her swatting,ect.

It may just be they're reacting to some simple change. If you change something in your routine, their routine, etc cats do react.

I agree to try Feliway diffusers, or Rescue Remedy drops. Try feeding them seperately. Food can create massive tensions.

It may sound strange but I think it's actually a good thing that Suki gives as good as she gets, at least sometimes. I think it would be more problematic if the tussles were almost always one-sided.

Try the Feliway (it lasts a month) and/or the Rescue Remedy. The worst thing that could happen is, they have no noticeable effect and you're out some money.

Sometimes two cats just don't like each other a great deal, but can still comfortably coexist for the most part in the same household. The fact that they're sisters doesn't in and of itself mean that they are supposed to be bosom buddies.

Please let us know how things go.