Anticipatory Indicators

During ‘real time’ moments like that . . .when you see any time of anticipatory reaction from Rosie, enter ‘training mode’ (as it sounds like you did). Check Addison; have Rosie sit and watch, and RICHLY reward. (yes, I would have rewarded at 85 IN THIS SITUATION . . . for her approximation of the proper behavior)

*INITIALLY*, there will be moments like this . . .moments when you won’t be sure if she was onto something or if it was coincidence or an accident or wishful thinking on your part. 

*INITIALLY*, don’t question her motives, just reward her. Regardless of the WHY at this stage, the WHAT has indeed happened: something in her behavior caused you to stop and check Addison. That is the beginning. 
WONDERFUL. 

What alert signal will you select for Rosie? Do not complicate life and think about an alert for low and an alert for high and an alert for ketones and . . . . 

Just decide on one simple behavior that can clearly communicate that there is a BG event and it is time to check.