New kitty

Question
I was feeding a small black kitty outside and she came up and actualy lt me pick her up.  I've had one of my cats disappear about two months ago and my other cat, Samme, who is roughly 20 pounds is about 5 years old and has always lived with another cat since I adopted her from the shelter four years ago.  
This time however, she is aggresively going after the new cat, Maggie who has taken a long time to overcome the fear she had of humans to start with and was living outside for who knows how long.  The vet gave her a clean bill of health and she is in her own room with the door open and a gate (which Samme now climbs to get in after her)  Samme obviously knows when she is doing wrong in going into the bedroom because if we see her she slinks off but she got in there this morning at 3 am and scared Maggie and woke us all up.  I don't like hitting but this is making it tougher to have Maggie accept her new home and I don't want to give her up because in the past altho Samme hasn't always been sweet to the other cat (she was when I originally brought her home to be a companion to my 18 year old cat -- she was very sweet and respectful) but with the others she was hissing/attacking but not nearly like she is now.
Should I be smacking her or ???  Because telling her she is a bad cat isn't doing it.
Any help would be appreciated.

Answer
Hi
firstly can i say you should never smack an animal, it is cruel because unlike humans they do not understand its meaning. All it is to them is pain and fear and will not stop the behaviour. if you are interested i do have a page about cat discipline on my website here

/cat-discipline.html

As for your situation with your other cat. there is a slow process which does help them to build confidence with each other without the fear of a fight etc. it does take some time and needs to be done slowly and calmly but it really does help the cats in the long run. However there are never any guarantees that they will ever live in harmony together and sometimes the best you can hope for is a sort of truce.

here is my page about the cat introduction process

/introducing-cats.html

best wishes Kate