(Long post warning as several factors to consider)
We have a rescue cat (about 6 years old) who we got as a kitten with her brother at about 4 months. They settled in with is quite well, her brother was the more sociable and she was always shyer and avoided visitors or loud, sudden noises/movements but otherwise fine and no issues behaviourally
About 2 years ago, we lost her brother and she seemed lonely but coped and we didn't look to get another cat as we had a house move planned, that happened about a year ago. Following the move she has become very much an indoor (upstairs) cat and the closest she got to the outside was sitting at the back door watching us in the garden, she has slowly got braver and will now venture outside carefully on her own but doesn't go far. (She may be more nervous of the outside as she was clipped by a car about 3/4 years ago)
As she appeared to have settled we did get a 2nd cat (kitten) and after initial scuffles they appear to have settled together but she will mess and spray in the house.
The house is over 3 floors and other than messing upstairs during the settle in period she does only spray/mess downstairs.
We have a litter tray in the downstairs toilet which both cats use overnight and as she was messing in the hall we added a second litter tray there to help (both cats have free access to outdoors as well) but she has now started to mess and spray in the dining room
I have throughly cleaned and deodorised but she keeps at it daily.
I am tempted to try the Feliway diffuser in there but they aren't cheap and on reading up I see suggestions that it should go in the room she feels safest in (our bedroom)
So - questions for those with experience;
Do you think it might help?
Should I get 1 or 2?
And, as I have reacted with asthmatic type symptoms to plug in air fresheners, I am wary about plugging anything in to our bedroom so do I need one in there?
Thanks to anyone who gets through that back story and will offer opinions and advice.