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You're a very caring, kind, cat parent to give this furry girl a home, when her previous owners had to move and couldn't bring her with them! : )
It's very natural, as I'm sure you know, already being familiar with cats and their ways, for her to be stressed and a little frightened in her new environment, especially because you have another cat. If she wasn't treated well by the cat she used to live with, she thinks this is going to happen all over again and that is why she is hiding and staying in a 'safe place' in the storage room.
Just the fact that you were able to pet her a little and she actually stayed on your lap for an hour, is a testament to the fact that deep down, she WANTS to be loved and trusts you enough to handle her and hold her.
It's still early in the introduction process, so patience is the key, and from your description, you're doing wonderfully, in showing her patience and kindness.
I'm glad that when your other cat is not around, she's able to enjoy full roam of the house, and since your kitty sleeps with you, she can explore, at night!
There are great tips and techniques on new cat to resident cat introductions at the following site, however, since the newbie is staying in the storage room, the 'sniff' under the door and 'see through a crack in the door' won't apply, but take what you can use from the tips. I always like to start with the 'scent transfer' method. Even thought it's not day 1, you can still use these methods. Take a slightly dampened cloth or paper towel and pet one cat (if you can reach the new one, or do this when she's out, roaming the house and your other cat is in another room) and then pet the other cat, then vice-versa. This will deposit each cats' scent on the others' fur so they smell each other on their fur all the time. You an also pet both cats with an old t-shirt of yours, so they smell your familiar and comforting scent and will both smell the same. Do this frequently throughout the day.
Feliway plug in diffusers are an excellent product to use in new introductions; it emits cat calming pheromones that help to reduce stress/anxiety. They are available in most pet stores, vet offices and can be ordered online.
Since she's on a shelf where you can't reach to pet her now, don't push the issue, however, visit her several times, gently speak to her, repeat her name a lot--this will help her feel secure--and offer her a cat treat and/or an interactive toy (feather wand/fishing pole toy), dangling it to stimulate her interest. Just do this for a short time, several times a day, and if she shows an interest, continue for a while. She's hiding there, because she feels most safe and secure.
Right now, you're doing everything right and I hope time and these suggestions will help your furry new addition start feeling more comfortable in her new home!
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