Sophie is learning higher reasoning, apparently. After calling Mommy and talking for a while, she said goodbye and hung up the phone. When Grandma asked to talk, Sophie explained the situation:

Sophie: Mommy hung up. She doesn’t want to talk to you.
Grandma: Why doesn’t she want to talk to me?
Sophie: Because then I’d have to eat before I play.

Naturally, if Mommy got involved, Sophie would have to follow her usual rules, even under Grandma’s care.  She gets a lot of credit for reasoning that out, but she still needs to work a bit on subterfuge.