Hello Mr M.
It might be easier on everyone if there isn't any pressure for the two women to be friends. It might happen in time but just because you love both of them doesn't mean that they will be able to get along with each other.
Also you said that in the past it wasn't fair that you kept your wife in the dark because you didn't give her a choice in the matter. I'm not really sure that she has a lot of choice in the matter now either. It seems to me that you have sprung this on her and just asked her to accept the whole situation as is.
Why are you uncomfortable with her seeking a second relationship? You know that you can love two doesn't it make sense that she would be able to be in another relationship and still love you too?
Everything will be ok in the end. If it's not ok it's not the end.