hanging my tomorrows on the bones of yesterday

Oooh now you're making me think that it might not have to be Jarvis who catches Nat out but Pepper's enhanced abilities because of Extremis. She's got heightened reflexes that could also mean heightened input receptors that catches Nat's smallest reactions to things. Maybe Nat's not 100% happy about this and that triggers Pepper's insecurities about her power. Sorry, this probably isn't helpful considering you've already chosen a course of action! Ignore me.