Sam shoves her hair mostly because of jealousy in Freddies face after he says he does not feel bad for her sign getting ruined. Freddie wasnt happy when Sam didnt say please to him. Sam tells Freddie to turn the camera to himself and say yo to the people.

Why does Sam insult Freddie?

Apparently, Sam thinks people screaming at each other is fun, meaning she probably has fun fighting with Freddie. When Sam insults Freddie, he actually stands up to her (as a true friend should), even though he knows she could beat him up (and actually has in the past).

Does Freddie care about Sam?

In iOMG, it has been confirmed that Sam is indeed in love with Freddie, as she made a move and kissed him. Freddie further reiterated this fact when he replied Its cool. after Sam apologized.