New cat - acting paranoid and scared after much initial confidence

Question
I adopted a new kitty 6 days ago from a local kitty colony.  My other cat recently passed away and I wanted to adopt another sweet playmate for my 8-year-old cat.  Our new kitty is a brown tabby (just shy of one year old), so we named her Mocha.  She has been so loving, affectionate, social, sweet, energetic.  She had seemed to fear nothing.  I have been shocked by her confidence, quite honestly.  The first 4 days at my home, she jumped up and checked everything out with confidence - even odd things - the dishwasher, the garbage can, the toilet as it flushed, has sniffed out every single room without hesitation or fear.  She met my 8-year-old cat on day two in the house.  There was some initial hissing, but by the next day, they were already playing and chasing each other around happily.  Mocha comes when I call her and loves being pet and loves jumping up and riding around on my shoulders.  Here is the issue: yesterday, when I got home from work, she seemed very scared of my bedroom (which she loved before - she had just cuddled with me all night the day before in the bedroom).  I feel like something traumatic happened to her while I was at work.  She won't go near the bedroom now.  I tried to bring her in there once and her hair spiked up and she ran out growling.  I gave her some space, then tried to gently pick her up an hour later and she jumped about 3 feet in the air!  I haven't let her outside and nothing could have come inside.  She still gets along happily with my other cat.  The past day she has been walking around low to the ground and is very hesitant and paranoid.  What in the world!  This is so strange.  What can I do?

Answer
Katie,

My best guess would be that maybe Mocha heard something like a car backfiring or neighborhood children with a cap gun...Outside noises can affect kitties especially former outdoor kitties who are used to being able to check out what caused them and now are indoors and unable to investigate. In terms of helping Mocha to calm down a bit I recommend that you try a homeopathic remedy called Bach's Rescue Remedy. You can generally find Rescue Remedy at health food/natural health stores. Rescue Remedy is a blend of flower essences that helps to reassure and comfort those who are fearful or who have been through a traumatic event. I do think that in combination with patience, gentle handling and distractions (play and foods like tuna and sardines work well) Mocha should come back around and be back to the friendly and loving kitty she was yesterday. I should also let you know that new cats should be quarantined until they are vet checked and tested for contagious viruses or infections. I have recently received correspondence from a person who was not aware of the need to test for or vaccinate against illnesses like Feline Leukemia. This cat owner wanted to make sure that her kitty didn't die in vain and that other cat owners were educated so that this tragedy didn't have to happen again. Unfortunately this person's cat passed away a few days ago and up until a day or so before the kitty died the owner was unaware that their cat had feline leukemia. You will want to make sure that your kitties are tested for feline leukemia and other viral infections that can be fatal. If your kitties are both negative you will want to be sure to vaccinate them both, if they are positive you should know that you may face the heartbreak of a seemingly healthy cat who all of the sudden becomes seriously ill and either dies or needs to be euthanised. You will also need to make some tough decisions if one kitty is positive and the other is negative for these viral infections. I do hope that all of this information is helpful. If you have any further questions or concerns, please do not hesitate to contact me again.