As a woman I can tell you the same thing I tell my husband that size is nice but what really matters is the talent you have on how long you can last and how you use it.This sort of find can go 2 ways, either you both argue, or you have an honest conversation.
There is nothing wrong with her wanting to see another guy’s dick.
Has she ever mentioned to you the need for a bigger cock? Or perhaps for being the subject of another man’s attention?
I would keep an open mind, many men would love to be in a situation like yours where sexual subjects with other men are initiated by their wife.