In my experience I agree that this should not be done secretly and the only time I am recommending this is when this woman is going to talk to this man privately. I think this has to be done where others can see them and so she needs some protection.In my 30 years in church, it is better not to record private conversations, which will start disrespect, suspicious....
If someone announces to record, we will tell him not to do so. Otherwise the conversation can't continue.
It is a common practice not to record conversations.
Also, in my experience several times I have gone to the leaders assuming they would support me only to learn later they were the ones involved in the crime (this happened in both the world and in the church). You should not assume that the leadership of the church is not aware of this man's behavior, he did this in public at a funeral, everyone could see.
I was in a church where a leader in the church learned of another leader's sins. This man was then publicly slandered so that anything he would then say would be discredited as "sour grapes" and then kicked out of the assembly and everyone was warned not to talk to him or his wife. The truth did not come out for another few years as more and more of our faithful brothers were excommunicated as they too learned what was going on.
What this woman saw was on display for everyone in the church at that funeral to see, it was serious enough for people to be uncomfortable but not serious enough that it can't be "laughed away". I would not be surprised if the purpose was to flush out those who have a problem with fornication in the church. There are a lot of churches that have been coopted by FreeMasons and I would not put anything past them. Slandering this woman would be the tip of the iceberg.
That is why she must follow the Lord's directions to a T. If she tells others then she is a gossip. If she goes to this man in secret she will be slandered. She has to speak to him directly, one on one, but she must have the entire conversation recorded so that they cannot lie about what was said. And it must be done in public at the church so they can't make any other slanderous accusations.
Luke 21:16 And ye shall be betrayed both by parents, and brethren, and kinsfolks, and friends; and some of you shall they cause to be put to death.