I have a female and male cat both of which are fixed. I just recently had my female cat fixed about 2 days ago. She is constanly hissing and whinning at my male cat. I don't know what to do about this. Is she ever going to stop? Before this both of them really got along well. I know it might to soon to ask this but i'm just concerned. I just don't know how long this hissing will last. I know she's in pain but i also feel bad for my male cat.
I know you are worried but unfortunately it may take a little time before harmony returns to your cats relationship.
One of two things ha happened, either like when we are in pain we get grumpy and irrational, your female cat is taking it out on your male cat. if this is the case as she begins to feel better this should stop.
Or your female cat is suffering from what i call trauma aggression. this is when something happens which frightens the cat, like being stood on or a loud sound and for some reason they associate this trauma with the other cat, often for no reason, but i have come across many such situations. So it could be that the stress of going to the vets and having the op has caused her stress which has frightened her and now she is reacting aggressively because of this stress. It may be a good idea to keep the two cats separate for a week or so, perhaps put your female cat in a warm comfortable room with her toys, bed, litter tray etc this will give her some time to calm down and to get over her operation. It will also stop her reacting to your male cat, this will be good for your male cat too. then after a week or so reintroduce them as if they had never met before, calmly, supervised and for a short period at first etc. See my page regarding introducing cats /introducing-cats.html.
I know this may seem a long process if sometimes this is the only way the situation is over come. Basically if you think of the fact that your female cat is frightened and she needs time and space to relax, then you will feel less stressed yourself, this is also something which your cats can pick up on.
i hope this has helped :)