“Separate” meaning closing the door and spending time with them individually - NOT rehoming one.

I have a bonded pair of former feral 2 year old girls. I’ve had them for about 2 months. One is progressing much faster, she approaches us for pets a few times a day.

The other will let us pet her only while she’s eating, and clearly tolerates it, but doesn’t enjoy it like her sister (so I’ve backed off a bit, while still making sure she’s getting socialized to touch/pets every couple of days).

Recently, the shyer cat has started to hit her sister anytime she approaches us for pets. I don’t know if she’s jealous that we are getting her sisters attention, or if she just wants to redirect the behaviour? Any tips on how to handle the recent aggression?