well... if your comfortable with him and her being together... thats cool. That should be enough right there. I know we've had ladies want to be with my hubby and i just didnt find myself attracted to them. So it ended up being him and her physically.. and me and her being friends. Which was fine with me.
My point is you shouldnt have to feel like you MUST meet someone you dont want to. It should be only if YOU feel comfortable with it. Cause trust me if you do it and your NOT comfortable with it... and they are lovey dovey in front of you..... you MIGHT find yourself in a tight spot... meaning if your anything like me and speak your mind.... you might find yourself saying something before you can help yourself lol.
So rather than do all that mess. I'd mill it over some.... maybe talk to the woman on the phone or email... that way you two can talk.. and get all the issues out of the way first. THEN if you feel comfortable(this might take a good while) meet her.
This is just my opinion... you can do as you see fit on it all.
Also.. your SO.. must understand that you may never feel comfortable enough to meet his GF. And if not... that should be ok to.