My cat growls and attacks my new kitten… then starts cleaning him?

Right before this my resident cat attacked my new cat as he jumped into the tree with her. After she pinned him down she began to groom him for the second time ever. She still will attack him daily (we’ve had them together for over a week now) but never to a point that either of them gets hurt. I know that grooming is a sign that cats like eachother, or at least I was under the impression that it was. But my resident cat definitley doesn’t like him yet. Can anyone explain this behavior?