how should they relate

I think you don't know about Christianity life/culture. You don't know the meaning of fellowshipping among Christian and non-Christian people after the worship services ended. It is nothing wrong with it!

Some single Christian female talk to married Christian male whose wife are present at church or vice versa---all know each other very well as long-time church members. What if they are all same school they all grew up? What if this single Christian female is volunteering in youth ministry to babysit those married couples' children where married couples know well? What if this single Christian female is homeless where married couples is willing to take her home to their place very friendly.

Nothing wrong with my Pastor chitty-chat with beautiful Christian women while the first Lady (Pastor's wife) chatting with young single man. Because both Pastor and his wife has LICENSED MARRIED COUNSELOR degree and they have rights to check out caring those Christian people's emotional needs unconditionally love---the same way as Jesus gave unconditionally love to everyone else NO MATTER WHAT!!!

In church environment where everyone fellowship after the service ended is safe talking openly where everyone see each other, unlikely one of them (single Christian female and married Christian male) take to the private room somewhere alone behind everyone back upstair that is different story (suspicious)!

So this ain't forbidden paradise to every bare Adames and Eves on the Fruit Garden.

What about church choir? Does it means you, as single Christian female choir, are not allow talking to married Christian male choir if the music director chose you to work with married Christian male choir as duet solo for rehearsal in preparation for special church service? 

It ain't a segregated gender churches!!!

plz explain further

pls explain further