Some buns are pretty territorial. Is there any way to block her view of the new bun? That might help calm her down. She’ll still be able to smell him, but it shouldn’t aggravate her as much.
Are you entering her cage/space when she’s charging you? Or is it when she’s out for run time? If it’s the first, try just leaving the door/gate open so she can come out to you. If you need to get into her space, wait for her to leave before you go in to move things around for cleaning etc. Most important thing is staying calm around them so it sounds like you’re doing well. You can also try giving her a small treat. That works really well for mine.
Are you planning on neutering your boy? They usually have a better time bonding if both are desexed. If you are, it’s best to wait until after he’s healed from his surgery before you begin bonding them as you often have to restart once they’ve been desexed. (I don’t know why that is as I don’t have any personal experience. Maybe from the prolonged time apart or their smell changes from the hormones?)
In the meantime, I’ve had success switching my buns litter boxes every few days. I clean it out, refill them, then swap them. It gets them used to the other bunny without having to interact.
PS Welcome to the forum!!!