I used to have 2 cats, a female and a male, that never liked eachother. The male was very old and, we believed, had some kidney problems. Recently, he ran off into our woods to die away from everyone. Now, our female is our only cat and she is acting very strange. She is not as hyper as she was and she's laying and sitting in the places that our male used to sit in, which she had never done before. She hasn't lost her appetite, thankfully, but I'm worried about her. I love her very much and don't want anything happening to her. Is there anything I can do to help her feel better?