Cat aggression in kitten toward cat

I'm reading many of the articles online as far as what to do if you have cat fighting - aggression with cats. My Cat (Lacey) is about 4 years old and my kitten in about 6 months old. My kitten (Emmy) is the one who is attacking the older cat. I have used seperation and a squirt bottle. None of which seems to work. I let the kitten out of the bedroom after a time out and she goes right back to attacking Lacey. The spray bottle does not really work at all. The one thing I have not done yet is spay the kitten. I'm hoping that will have a positive result but beings the behavior has already developed, I'm wondering if this will really help. I'm wondering if catnip will help and if so is it safe the give to the kitten. I'm open to just about any other suggestions.

 

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