Something else I just thought of, though I've not seen the movie yet so don't know what they do. They could have completely missed giving a positive message of if there is something you do not like you can either go to your parents about it or if you don't feel comfortable about it go to a trusted adult, in this case Littlefoot's grandfather, one of the 'leaders' of the great valley and tell him about it. Though it may make more sense with considering how Cera's personality is to have her tell her friends, have littlefoot go tell his grandfather then have Littlefoot tell Cera what his grandfather said. Or have Cera alone looking upset walking around and obviously upset and have Grandpa longneck happen upon her, so she didn't go to him, but just happened to meet him, which would still fit with her likely not going to him since in this case she could happen to meet him and answer his question of why she looks upset about something.
A sidekick character, maybe, but 2 of her roles is as the cute baby, little sister.