Adult Cat with hyperthyroidism

Question
I have an adult cat (14 yo) who was recently diagnosed with hyperthyroidism.  She is on medication and seems to be doing well.  Prior to her diagnosis, about 2-3 months ago, I lost her friend, another adult cat (12 yo) to cancer.  Because my 14 yo was grieving, my sis in law, a veterinarian, suggested I get a kitten, since she probably would not tolerate an adult cat in her territory.  There has been some difficulty in her getting used to the kitten, who is now 4 months old.  She was semi-starting to toy and play with him, but passive-aggressively.  She always slept either on the bed beside me, or under my bed, but as soon as the kitten came, she would stay under the bed 90% of the time.  Now, she is hiding in the back corner of my closet, and will not come  out.  I have started putting the kitten in another bedroom at night, but she still will not come out, unless I drag her out.  I fed her this morning, and she ate, seemed fine, but could not get back in the closet fast enough, even with the kitten locked out of the room.  She was in my closet when I left for work, even though I left the kitten in the other bedroom. Is this "normal" behavior, or could there be something else going on with her?


Answer
Hi
I don't want to contradict your friend but i would not have suggested getting a kitten so soon after the death of your other cat if at all. Cats need time to grieve as well and by bringing in anew cat into the house it has added to her stress. Also because of the age of your cat i would have said that the last thing she needed was a young whipper snapper invading her territory.
I think her behavior is completely normal for her age and circumstances. She is not feeling as young  as she used to her and she probably feel that her territory is now threatened as well.
I have written an article about cats grieving, it may be of help :)
http://ezinearticles.com/?Do-Cats-Grieve-For-Their-Feline-Friends?&id=708972