Tiki is acting this way because she feels very stressed and anxious in a new environment with a 'strange' cat she doesn't know.
First, bring her, in her carrier, to another room with a door and open her carrier to let her out. Then, put food, water, litterbox, toys (not from your cat), cat bed (if she has one), into the room. The cats need to be separated for at least a week, so this will be her new home for that period of time.
There are some great tips and techniques for new introductions. First, I recommend the scent transfer method: take a slightly dampened old washcloth or paper towel and pet your cat, then pet Tiki, then vice-versa. Do this frequently throughout the day, so they get used to each others' scents. The following sites provide a lot of information on new introductions, that you will find helpful:
In addition, get some Feliway plug in diffusers; these emit cat calming pheromones that help with stress and are great at times of new introductions. Here is more information:
Since Tiki is normally a high-strung/nervous cat, the introduction period may take some time, but if you are patient and take things slowly, eventually things will start improving and you can hope for the two cats to at least tolerate each other, even though they may not become best friends. Hopefully, they will become friends, but older cats usually are set in their ways and find younger, more energetic cats annoying.
You can also use some OTC cat calming remedies that are taken by mouth. One, is Rescue Remedy for Pets and the other is Composure chews. Choose one to give and don't give both. Here is more info:
I hope things go well and soon, Tiki will become part of your feline family!
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