I feel sorry for the new lady in your friend's life. She must be very anxious about meeting you,and it is hard to step into a set up where everyone but you has known each other for many years and has a shared history. I have a friend who has made a very happy second marriage to a widower, but in secret she has said to me that she is very aware that she is only there, with him, because his wife died. So, my advice for what it is worth is to be the kind and thoughful friend that you are, make them welcome for just a short stay, be flattered that he wants to share his happiness and make his new partner welcome, take them out and about. You may develop a new friendship!