I've posted before about aggression between my two female cats. This is settled down and they have learned to tolerate each other in very small doses (Older cat lives downstairs, younger cat upstairs).
Recently, the younger cat has been spraying upstairs (not where she eats or sleeps). Is there anything I can do to prevent this? I have a Feliway diffuser which seems to help the older cat more so than the young kitty.
Also, there are alot of stray cats in my area that she watches from the window so I'm guessing this is linked to her behaviour?