Introducing New Kitten to Resident Cat?

My 15-month-old snowshoe seems appalled by the addition of a four-month-old kitten. Rochelle is very high energy and has a strong predator instinct that I help her give release to by providing several cat trees and daily prey-catching opportunities with wand toys. I am afraid she might get stuck alone at home if I get stranded outside of my isolated home location with only someone to come in daily to feed her. I wanted her to have a companion because she loves to play nonstop. Being alone would definitely be hard on her, and just being given food and water daily wouldn't be enough.

In comes barely-four-month-old Delajune. It turned out she was sick from the shelter, plus having a new spay, Delajune didn't play at all. I accidentally introduced them early, so afterward, I let them spend time in each other's company closely supervised. Each has a room the other is kept out of, but they share all the main living space and enclosed outdoor patio, usually at different times, but both of their smells are out there.

Rochelle has never "puffed up" around Delajune, not even at their first meeting that I am aware of, but she invariably works into a predator mode where she stalks the kitten, pounces on her and bites her. Initially I was angered by this and punished Rochee, but no longer. Now I accept her aggression and merely separate her from the kitten when it manifests, which is every time she is around her for any longer than 10 minutes, and sometimes it doesn't even take a minute. It has been a week last night, eight days total. Today, I let Delajune out of her room and Rochelle came over and groomed Delajune all over, very calmly, then they both ate out of the same bowl. I thought things were getting better, but not five minutes later, Rochee attacked Delajune, had her on her back, and was biting her stomach. She didn't bring blood, but she wasn't playing, either.

So, what about this situation? I have been reading about introducing new animals (should have read articles first instead of after-the-fact!). I am not sure how to proceed, or what to expect. Will it ever be safe to leave them alone together, or will my adult cat always be prone to be overtaken with ambivalence and unpredictably attack the kitten?

My cat has five big cat trees, so there is tons of stuff for them to share, including toys, boxes, and many cat tunnels. I have also kept giving Rochee attention so she wouldn't feel a loss of importance because of the little cat. Nothing seems to help. I won't risk her hurting the kitten, and am certainly not going to allow a continuing bully relationship to become established. The kitten is sticking up for herself now, is not acting like prey to Rochee's predator.

It is the grooming and then attacking only a few minutes later incident today that has got me the most worried, because how will I ever guage what the status of their interaction will be from moment to moment and be safe leaving them alone together? Rochee is a very athletic 8-1/2 pounds. I am guessing the little cat will be much bigger than Rochee when grown: longer, taller, and heavier, but right now she is a waif in comparison.

Thanks for reading. I am preparing to find a good home for Delajune if this doesn't work out, and am not sure how long I should give it.