Odd Behaviour

Hi, my mother cat is behaving very strangely.  She is 5 now.  She wants to go out, come in, go out, come in ...... She goes to the wrong side of the door, goes to the wrong window to be seen to let in  I am loathe to take her to the vet at the moment as she was a rescued cat and is extremely nervous of anyone or anything out of her routine.  Just wondered if anyone had any ideas?

Any change in behavior like this warrants a trip to the vet.  I'd ask them to run blood work to see if she's got anything going on medically like a urinary tract infection or something like that.

Is she fixed?  Is there something outside that she's interested in?  I might follow her outside a couple of times (or spy on her from inside, if you can) and see if she's getting into anything.