Advice on fostering kittens when one cat isn't happy about it?

I have been fostering kittens for about a year now. I help out a great non profit organization that take in kittens from barns or bad situations and put them in foster homes and give them shots and vet care. I really love it and feel like I am helping animals in need.

The problem is - Pixel. She is my 2 year old calico and she hates other cats/kittens. I have 2 other cats, Kyo and Shadow. Shadow is 14 and doesn't really care one way or another and Kyo is 1 year and absolutely loves the kittens and plays with each and every one of them. He even looks around the house for them when they leave.

I don't want Pixel to be upset, however. I do my best to make her life happy. I have a giant cat tree, shelves on the wall just for the cats to sleep on, and a lot of little scratch pads in each room. I even made her a little bed on a shelf on top of the fridge cause she seems to like being up high. I play with her but she gets upset with the kittens, I lock the kittens up so we have one on one time but the kittens get upset. I recently even built a "catio" attached to the window so she could sit outside whenever she wanted but that only seemed to make her realized there are neighbor cats and now she is obsessed with looking out the windows and get pissed off when she sees one. My window is basically in the neighbors yard so there is no hiding it. I put up bristleboard on all the windows so she couldn't look out T_T

I'm kinda at a loss now. I feel like I've done everything I possibly can to make her happy. I really don't want to give up fostering as the organization really needs the help but I also want my cats to be happy. Pixel recently got urinary crystals, the vet originally thought it was from stress but when they found all the crystals they said it's something that just happens to some cats. I'm a little worried the stress caused it though. She is on special vet food now.

Can anyone please offer any suggestions? Has this happened to anyone where you were able to help the cranky cat be happy? I plan to take a few weeks break after my current 2 kittens go to give her "time off" but I am hoping to foster again. Usually I don't have the kittens long but these last 2 I've had for 3 months now. Not sure why no one wants them!!

Pixel, oh how we wish you could talk and explain what is wrong with having wee kittens in the house!

How does Pixel respond with your other 2 cats? Does she ignore them? Does she terrorize them? Was there an adjustment period?

I'm sorry I don't recall how long you've had Pixel. If she was fixed recently, it can take 3 to 4 months for all the hormones to work out of the system. That may be a help; or not if Pixel was fixed long ago.

How wonderful that you foster! I failed fostering each and every time . . . cats, dogs, fish, I kept ALL of them! And I know the rescues always need the help.

Would love to see some photos of the catio, the wall shelves and so on. I take it Pixel loves all of those?

Stretchy cat collar.

Feliway.

Put the collar on Pixel. Twice a day shake the Feliway well then carefully squirt some into her collar.

See how that works. It did wonderfully for Oscar years ago when he had idiopathic (stress-caused) cystitis. Very few crystals but lots of inflammation and blood in the pee.

Pixel might not ever be accepting of the kittens. Cats are very territorial. Even though she had crystals in her urine, I'm sure the stress made it worse.
I agree with Candace: Feliway might help, it also comes in a diffuser you plug into an outlet.
Also calming treats like Composure are an option.
If you are not giving up fostering (which is a wonderful thing to do, but might be the only way to make Pixel happy again), make sure to watch out for other signs of stress in Pixel, like excessive self-grooming and changes in appetite.
You are already giving her as much attention as possible, keep that up, even if the kittens get upset.
Good luck to both of you. Pixel, I know how pesky kittens can be.;)

I've had pixel since she was a kitten. So, 2 years. She was spayed at 6 months. As a kitten she loved my older cat and they played a lot. Kyo is my foster fail, she hated him at first but now (as long as no kittens are around) she plays with him often. The older cat recently started to pick on her for some reason. No idea why. He just bats at her and she meows and hisses when he does that.

I have heard of the feliway thing. I'm saving up to buy one. Unfortunately short on money right now. Pets are constantly getting sick on me.

Right now pixel is snuggled on my chest purring away. She's more of a people cat. Especially to me. She loves to snuggle me and has to be on me at all times.

Her health is otherwise fine. She is over weight. I'm trying to deal with it but it's hard because I like to leave food out for the old cat. He only wants a little at a time and is getting very thin so I'd like him to have access to food when he wants but she gets into it. I put it up when I'm home and feed him several times through the day but I can while I'm gone all day at work. I have 2 microchip feeders but one is for her (vet food is expensive and fosters eat it) and the fosters had the other (so they can eat as much as they want without her always eatting it)

Hopefully I can buy a diffuser soon and try it. Where is the best place to put it? She seems happiest in the bedroom but I need to close the door at night otherwise I'm woken several times. So I could put it where she sleeps the most otherwise?

The diffuser should go close to where Pixel likes to spend most of her time. Amazon has the best prices for the diffusers.
I hate to mention this, but you said that your older kitty started picking on Pixel, and he's getting thin. Both of those things might be signs of a health issue.

I've taken him to the vet for blood work and tests. They said there is nothing wrong with him. He used to be really fat, around 18lbs. He's now around 11. This has been over years he lost that but the vet said the blood came back fine. He's not aggressive he just swats at her and chases her but not hissing and growling. I was thinking it was maybe she was acting a different way that has him doing that.

He also used to sleep all day and now he plays with toys which he never really used to. I actually thought he looked more active. People tell me he doesn't look 14 at all

I'm glad that Shadow checked out ok. I'm sure that the weight loss helped him being more active.
And you're probably right that he's reacting to Pixel's different behavior.