Maybe, .. i just had this thought last night..
but..
maybe there wasnt anything significant said or done when the ' other mommy' showed up, but just the simple ACT of her shoing up off cue, and out of nowhere was what set Mo off. Made mo feel insecure like she could do this anytime.
To top off the fear of having her show up on the doorstep, mo had to get in the car with her.....
![Shocked](https://cdn2.able2know.org/images/v5/emoticons/icon_eek.gif)
according to a young child, getting in a car means GO.
Mo might have taken that as an unarranged trip away from you boom, that may have ment " no return".
If that is the case, then that is a normal reaction to any situation. Trusted person or not, having someone show up and take you somewhere is a bit nerve racking for kids.
Maybe.... just maybe.... mo's reaction is as simple an answer as that?