Sibling fighting

Ever since my younger turned 1 and started reaching for toys my older child who’s 4 will hit his head with a toy, kick him away, or basically move her body trying to block him from getting to whatever. We’ve tried to talk to her about, reinforce it’s not okay to hit, tell her she wouldn’t want other people to hit her, she used to laugh a lot when we’d bring it up and say she thinks it’s funny (even when he’s crying). We’ve tried to separate and give her space to play independently but they both have shared toys too. We talk about the rules before setting it up to share and it always turns into a blow up situation. I don’t know if it’s better to send her to her room (she usually won’t go) or just removing the baby (but I don’t want to reinforce the behavior). When will she realize it’s not okay or will it just be a thing cause siblings do that? Anyone with experience?