I understand what you are saying, but I am just forming a reason as to why she would even come to be relevant to the local plot. She clearly has no reason to be there as her boy toy has not shown any signs of rebellion and Mike is literally the one remaining thing keeping her tied to that place. Without mike being the trigger, she ain't going to be part of anything.
What she does from that point, aka try to worm her way back into Mike's life, is up for grabs to how Taeshi would want the character perceived. Is she remorseful and thinks she fucked up? Is she a manipulative bitch which will go all yandere on Mike's ass? Did her relationship with mike cause some sort of issue with her career and she is back in town a few months to let everything die down and now that she has nothing, getting back with mike is done solely to have something more than just existing?
And yeah, probably. But, as I keep saying, Tae has never hidden her skill or how she thinks about the story, so who is to blame for that?