Kitten fighting with older cat

Question
i have a three year old cat she has a flap and is inside and out.  shes a very independent creature and is really easy to be around. before xmas we rescued another cat (shes under a year old), we found her at the roadside. shes very affectionate and was definitely loved and looked after.  anyways, the problem is that shes constantly trying to get at the older cat.  she runs and tries to pounce on her.  the older cat tries to fight back but its just too hard to watch.  it doesn't actually come to blows but theres lots of hissing and screaming and the odd punch.  the older cat is ok with her being in the house, and really wants to get on with her own thing without being bothered. i've tried to keep them seperated but its been going on now for over three weeks and our house is in turmoil.  its such a stress trying to watch the new kitten coz shes into everything.  how can i get her to calm down and leave the older cat alone? we got the younger cat spayed at the weekend and she was a really good patient but shes is just tormenting the older cat. i've tried putting her outside for long periods so she'll tire herself out but this doesn't work as she just wants to be in the house fulltime.  i love her dearly but shes hard work. i've no problem with her being in the house if they could both get along.  i am at my witts end and i hope you can help me. .......... thank u. ......

Answer
Una,

I have two rules concerning cat inter-relationships.  (1) We humans do not understand how cats determine their relationships.  (2) Any human interference is always counter productive and will make things worse.

So, I would just leave them alone to settle things however they want.  Often we attribute human characteristics and motives to cat behavior.  This leads us to misunderstand what the cats may be doing.  It is very possible you are misinterpreting rough play for fighting.  Cats have exceptionally tough skin and are not likely to hurt each other with the behaviors you describe.  Cats also play very roughly with each other.

So in summary, I would not separate them and ignore any "discussions" they may have.

Best regards... Norm.