This has been my assessment for a long time. She was a large, unattractive, argumentative woman who had too much education and attitude to get herself a nice man. Then Rev. Wright fixes her up with this smooth, cultured, exotic guy who acts like a gentleman with her and she thinks she's struck gold. Remember that most gay men can function to some extent with women, so of course at least one of those girls is his; the older girl is the image of Obama. Who knows when Michelle figured it out? But now divorce is not a possibility if she wants to go on living. This certainly explains the separate vacations and constant travel.
Don't misunderstand, I believe she is a racist and an opportunist who is arrogantly squandering our money and her own position. I have little sympathy for her since she knew what he was long before he ran for the presidency. Just offering an explanation for a lot of things.
I think she has decided she is owed the travel and the lavish clothing because of what she is living with. Once he is no longer in the White House and cannot provide all the goodies, she may have to go find herself another sugar daddy ala Jackie O. She has to have a certain greed herself to have stuck with him this long.