I would try and let them get on with it, that's what I do with Jasper and Milly. I'm sure I read somewhere on a previous post that you shouldn't really intervene, obviously if they are about to cause some serious damage then that's different. Jasper knows sometimes not to make eye contact with Milly coz that will just make her go for him. This is even though Jasper is twice the size of Milly. I do intervene when Jasper is jumping Rosy, coz she's nearly 8 and quite frankly does not need the likes of Jasper annoying her, but she's accepted him anyway.
Milly is back to growling at him again today, so that glimmer of hope yesterday, was just a glimmer. I do feel a little guilty at times, coz if I didn't get Jasper then Milly wouldn't have these anger issues but I wouldn't swap Jasper for the world now. I suppose it's a bit like my two daughters who constantly bicker and fight with each other.
Good luck with whatever you choose to do, she is a gorgeous cat and I hope if given more time they will learn to get along.
Marie x