As I stated in my intro I have 2 cats... the one I am having trouble with is my elderly female called Creep. She is now around 14 and spayed, and WAS toilet trained both in and outside. However past few months it seems she doesn't care where she goes to the toilet any more. She doesn't ask to go out and simply picks some where (anywhere) in the flat and does her business.

So far she has done her business; on our sofa (4 times), in her and Quicksliver's sleeping area (lost how many times) and has just last week taken to doing it in their eating area. (7-8 times!)

I'm not sure if she is just being lazy or if this is a case of her not being able to control her system any more. She knows she does wrong since she hides after doing it, or just stares at me after I catch her... and Quicksilver knows too since she usually goes after her as if to tell her off for doing it.

I am at my wits end and have even tried using accident cleaner after she peed in the eating area today... only to have not even 10 minutes her taking a poop there.

I really do love her to bits and the only time she seems to bother using the litter tray outside is when I have the front door open 24/7. (which in the summer was all well and good, but now it's winter it's becoming impractical.)
I don't know what to do and feel if she keeps doing this I may have to give her another home... so does anyone know what's going on and how I can solve this problem? I love her so much and don't want to give her up, but I feel at this rate I'll have no choice but to do so.