When we adopted our third cat Winnie she was not socialized having been born in the wild and feral until she was 3 or 4 months old. She'd been adopted out and returned to the rescue league twice and when we took her home they told us to put her in the smallest room in the house and keep her there until we were able to pick her up. She stayed in the downstairs bathroom some months and when I could pat her a bit we let her out. Gwen has never accepted her and they have an ongoing battle for the position of top cat that doesn't seem like it will ever end now that we are several years down the road. When Winnie did come out Gwen proceeded to pee on the heater vent in that room in order to establish her dominance of the territory. It's never an issue in the warmer months but as soon as the heat comes on we must be vigilant. I know this is only her instinct but it's difficult not to get really frustrated with it. Last year went went the whole winter with no incidents of any kind which made us a bit lax this year so of course she slipped in and  left her mark, several times. Here's my new arsenal of odor fighters and cat deterrence. I know cats despise the scent of citrus so I found an orange oil based room spray and hope that liberal use of this will make the bathroom a very unpleasant place for her to be. I discovered that the baking soda and orange cleaner do a fabulous job of eliminating the odor should she happen to slip in there again.