Just trying to throw some "what ifs" out there, so I am just prefacing my post by letting you know I am not trying to be intentionally negative.
You have never met your online love. What if you meet and the chemistry in person isn't what it is online? Can I ask if meeting someone online was intentional, or was it a chance meeting - like you were playing online games together and got to talking? If it was intentional, is there a reason you chose to talk to someone that lives so far away?
Also, if things are as great in person as they are online, what are you going to do about it in the long term? Does she want to move here? Do you and your wife want to move there?
Sometimes it is hard to see past the NRE into the realities of the future. It sounds like your wife is more supportive of you being poly than your girlfriend is. I am assuming you didn't meet her in a poly fashion....?
I completely agree with Musical that your women becoming friends can make things MUCH easier. Maybe your wife can also speak to her online before you meet in person?