The only real possibility is that Michelle could be delivering a personal message from the President—a message he wants no one else to see or hear except the recipient. Maybe it has to do with Iran and a possible attack in the next few months. No, that's not the only real possibility.
There's a host of other means to deliver "personal" messages.
She is NOT a member of the elected government of our country, IF that still matters.
Why the silence in our press about her meetings with the named individuals?
You are assuming a lot. The fact is that the First Lady can carry a personal message from the President. It is done all of the time regardless of who is President. The issue is what kind of message could she be carrying. Moreover, she may not be carrying anything. A member of her party may be the one who is having clandestine bi-lateral meetings using the cover of the trip. That is far easier to pull off rather than doing it in the spotlight of a First Lady whose every move is being covered by the MSM and a Secret Service security detail.
She is NOT a member of the elected government of our country, IF that still matters.
There are plenty of members of our government who are not elected. In fact the vast majority are not. The office of the First Lady has a USG staff and is part of the WH budget. Presidents have been using private interlocuters for as long as I can remember to deliver messages.
There's a host of other means to deliver "personal" messages.
It depends on the substance of the message and how confidential you want to make it.