see, like, missy has been a very touchy character in this regen?
she snogs the doctor, and constantly rests her arm around him/on his shoulder (outside st paul’s, and once she’s free on the plane, to name a few times), and just holding on to him for dear life when he kisses her in the graveyard. she wraps her arm around osgood. in s9, she reaches into clara’s personal space to make her have the vortex manipulator, and she sits very closely to the doctor in the ship.
getting into people’s personal spaces is a very quick and effective way to make them very uncomfortable, and she uses this to her advantage to scare osgood, and her just being nearby people makes them nervous.
the scene in which she reaches for the doctor (and to me she looks like she’s reaching to fix his coat, like in s8 with the unit/cybermen in the square scene), he steps back, and it shows she wants to be near him and touch him for her own comfort, not to make him uncomfortable. she instantly stops, and freezes and looks down and laces her fingers together, kinda shakily. she doesn’t continue her attempt, which is something the old her might have done - stepping forward and not allowing a rejection in the first place.
[gif from @the-clever-boy-in-the-funny-hat]
12 recognizes, however, how much she needs that contact, but isn’t ready to give it. he’s not much of a hugging person, but he understands that she needs that from him, so he does what he can. her reaction to this, like she’s taking a breath, about to speak, is so fundamental. she knows he’s trying to help her too, but doesn’t know how to convey how much she needs it without embarrassing herself/acting ooc.
i feel that missy really needs that hug. she really, really needs it. even just from bill. she hasn’t really had physical contact with anyone in years, presumably, and that does things to a person whose character revolves a lot around it. she’s restraining herself so much.