I would have him have his own dating account. He can find his own girlfriend. Take the "we" out of it. I have discovered trying to make a quad work is as hard if not harder than a triad. If I was talking to a guy online and his wife was very involved it would be a turn off and I would be extremely leary about how much involvement his wife would have in our relationship. So my suggestion would be to back off, let your husband do his thing and maybe somewhere down the line you and she can develop a friendship.
Sue, hinge in a vee with Nate (Polysexual) and Sam (monogamous)