This stuff always comes at me in the shower.
Let's run with Michael having a strong bit of stalker in his behavior. It makes things easier and, hell, he's a control freak.
Michael and Trish's first meeting, change it out a lot. Michael admits to knowing that she's a tease - "You don't think the men here talk to each other?" (although that is not how Michael knows) - and calls her a coward, to boot. Patricia reacts as she usually does when caught without a leg to stand on / too infuriated to speak and walks out of the bar. An otherwise lovely conversation gone very sour.
Patricia has a rough day at the office - unusually vivid daydream/hallucination of killing a pain-in-the-ass client on the table. It's rattled her badly, and once she gets home, she's going to call in to take the next day off for mental health. She never takes time off - the office practically had to have an intervention to make her go on vacation - so this is an indicator of how off-balance she is.
Patricia showers, changes, idly contemplates going out, when there's a knock at her door. It's Michael, pretty much daring her to prove she's not a coward.
Initially, I had envisioned their picking up this thread in the bar, but that's not a setting that's good for confidences, and it would be all told and not shown.
I'm going to hold on to a scrap of a scene and see if it doesn't settle down somewhere, as it might yet do so. Gist is: Post-Huxhold-hallucination, Trish is at the bar, drinking club soda and hungrily eyeing the bottles of booze. Michael sidles up to her, puts a tumbler full of alcohol at her elbow and reiterates the accusation of cowardice. Patricia looks from the glass to Michael, very thoughtful. Cutaway to another jumbled daydream/hallucination - more disjointed that the one earlier, in the OR - of events following a very predictable course: Trish and Michael get drunk and ferociously naked. Trish abruptly returns to reality, pours the proffered drink into an ashtray and declares that she doesn't play bullshit games - if that makes her a coward, so be it. Michael has something pithy on this particular event being a win-win situation, but Patricia's not around to hear it. As I said, this might find it's way into the story, it might not. I can't have Patricia bouncing between the bar and the office too much - it's going in circles, not going forward. Moving the two of them to the more intimate setting of her home - simultaneously bringing up the mystery/threat of how in hell Michael got there - gives me a bit more wriggle room. It also helps decrease distance between viewer and character - or, at least, that's my theory.
So, it seems there is potential for Michael as agent of change, by being someone who challenges Patricia, and won't accept her usual form of behavior - avoidance, get-away/closer games and, when all else fails, sheer bitchiness. He's a deft enough manipulator of people to sidestep the usual traps and keep going.
Michael will bring Patricia to believe that what she wants is "real" control over her life, whilst taking it from her. Conflict will arise over the definition and nature of that control.
This still leaves the whole who gives a damn question unanswered but, fuckit, any brainstorming is good brainstorming.