I rationalize that Michael's emotions are all over the place because she was indoctrinated into a Vulcan lifestyle that humans aren't supposed to have. I mentioned elsewhere the way she deals with emotions now is like a kid denied the opportunity to play with super soaker toys suddenly being given a phaser rifle. Burnham kept a Vulcan like demeanor on the Shenzhou, but once the Battle of the Binary Stars happened she suddenly had to deal with emotions in ways that she never learned how to due to Vulcan conditioning
It can be a good explanation.
Like an "inverted" Spock.