My DS2 was often annoying DD4.5 too. Pinching, pulling hair, pushing, sometimes biting.
She had anger issues towards him too ever since he was born.
Things that have helped their bond (and it has improved a heck of a lot):
Getting DD to do things for DS like feeding him, putting on shoes, brushing hair, sharing treats....anything to promote sisterly love. She understands more at this age, its not because I'm showing favouritism.
I have taught my Ds2 to share e.g. I give him 2 cupcakes and say give one to your sister please. Then lots of praise once he has done it.
When we tidy up, I get them both involved even if Ds2 can only carry a spoon.
I take my DS hands and gently show him what physical contact is acceptable. Stroking her hand is a good start and then you can take it from there.
I encourage games like e.g. if you're happy and you know it give each other a hug. I might take a teddy and make it pretend to talk and sing to them, bop on the nose. Sometimes they take turns signing lines to a song or DD will leave words out and DS will fill it in. Or i might pretend to be a giant and stomp around the room while they run and hide away together.
Blanket games are great, e.g. they lie down on the carpet next to each other and I throw the blanket up and gently cover their face, rinse repeat. Yesterday i sat with both in my lap facing each other and a blanket wrapped around, little tickles and nose bops and they were in stitches.
On YouTube we watch Dannygo and they dance around together. They really love numbers so the Additions/subtraction one is also another they like to shout out answers too together.
Also walking together for brief amounts of time outside holding hands.
For times when they need separating, I would use a cot if you have one for mini timeouts (or any spot you feel works). Otherwise I just get DD busy in the kitchen and give my DS a puzzle to do. This works best for my kids to get their focus elsewhere.
It takes patience ultimately and can feel slow at times. But it does get better.
Good luck x