Of course, you should reassure her and tell her that everything is ok and NOT leave her sitting out on a limb ALONE! If she has never had aBBC it can be a very traumatic thing for some wives. Even if she has had BBC before she was married, having a husband makes a world of difference. Openly support your wife.
My wife doesn't have a collar but she does have some Queen of Spades jewelry that she wears on 'special occasions'. I bought that for her when she first expressed only the desire for BBC but before she had gotten one. For us, it was the desire that counted at that point.
Remember, unless you are being excluded entirely, what you two are doing is a team effort. Individual BBC will be there for a while and then drift away, but you and your wife will remain. I can't overstress the importance of supporting each other! Remember that there will be times when YOU are the one needing support.
What you are becoming involved in can give both of you great sexual pleasure and enormous emotional satisfaction, but it can also destroy your marriage bond and relationship if you fail to use common sense. Choose your new friends wisely and remember this: You and your wife/ then the new friend. The New friend will enhance your sex life, not replace it. I wish you two great success!!
I'll now pack up my soap box and fade away. LOL