If it is an accident, has anyone done anything about the kitten’s lack of toilet training?
There are some good reasons for this. First off, if your cat was litter box trained (meaning she uses a litter box – like any other cat would), you may want to reconsider putting her in with your new kitten because that can cause problems too.
Secondly, there’s no way to teach a kitten not to poop everywhere unless one is already litter-trained. And even if they’re both litter-trained (and they don’t always get along very well together at first), the little one will also sometimes leave feces somewhere he shouldn’t be so his older sibling has to clean up after him instead of watching TV or reading books or doing homework or whatever else cats do when they’re not pooping all over their owners’ stuff!
So… I’m sorry but there really isn’t much you can do about this beyond getting another pet and giving her lots of love and affection until she figures out how “cat” things work here 🙂