Proceeding with caution is always best, if there's a way you can get Olivia used to the scent of the new boy even before you bring him home, that might help. Do you have a room you could sequester him in where they could maybe smell each other under the door, etc?

It's one of those situations where you kind of never know until you try. I have know Siamese that were completely fine with any new cats, and others that disdained everyone but their human.