hi.....gets frustrating doesn't it, trying to understand why a kitty does what he does...ultimately she is trying to tell you something, and sorry but hate to say with 2 cats...they really really want each their own box. and I too know how hard this is, I have to put my second box in my small half bath...its not a very big box, but seems to make my kitties feel they have a choice now...
I will send you a link, not a whole lot of info other than what I've stated,,,,its either medical or behavioral, is she constipated by any chance?
http://healthypets.mercola.com/sites/healthypets/archive/2011/06/16/tracking-down-the-cause-of-your-cats-bad-bathroom-habits.aspx
Hi, at the very least you need to have 2 litter boxes. Actually, I've read that we should have a litter box for each cat we own plus an extra box. Also, make sure that you are cleaning the litter box every day to twice a day. Cats are very picky and are clean freaks. A dirty litter box is a major reason that they will go outside the box.
Do you have the clumping litter? Cats seem to like that litter much better, and it stays clean.
I've purchased a second litter box, so now the goal is finding a place that is appropriate. I do use the clumping litter (since it's easier to clean) and have been diligent about scooping it every day. I am hoping the second box will help! Thanks for your advice, and for the link!
Good luck to you.
Let us know how things go.