It depends how you feel about it. I am personally too cautious sometimes, and might separate at night for a while, others say just let them work it out. Only you can see if it looks to be excessive aggression or if it's just mostly noise.
Your existing hens see her as an intruder into their territory, so they are trying to drive her out. Your EE is running like she's supposed to but can't actually leave. Generally you should pen them side by side for a while until they get used to her being around. Otherwise what you are doing...