unusual terratorial marking, cat

I have recently taken on a new kitten, and I am having problems with my 14 year old (neutered) female cat. She hasn't shown much aggression towards the new kitten, but has started "marking her terratory" by deliberately peeing on doors and walls in the house. She just backs up shakes her bum and does it, just like a tom, with a defiant look on her face! I'm at my wit's end, and fed up with washing floors and walls. What can I do?

I had a cat a few years ago (wasn't well, so was pts :sad: ) and he did that when he felt scared or threatened...

Maybe show your older cat you still love her just as much and there is nothing to be scared of?

Sorry I can't be anymore help!!

Weedle :)