Why don’t you email her something short and sweet (not long and drawn out!) about you and your wife’s basic beliefs in plural (don’t argue it or it sounds like you are just justifying it), let her know what you’ve found attractive about her (hopefully it’s more than just physically), let her know she is free to ask you and/or your wife any questions she may have about it (because, let’s face it 99% of Christian church women will have never had plural cross their minds as being an option, or even come to desire it alone), and don’t throw out “you never have to speak to me again”- that’s an easy out and sounds a bit childish. Maybe even invite her to look at the forum for things she might be curious about, if the mods remove this section of convos lol. Obviously, if she comes back and says, no thank you,
leave it at that. No need to keep incessantly messaging her or you come across desperate/ someone she is glad she only gave her email to. That’s my 2 cents at least. Take it for what it’s worth