The blond girl is opening her drink as she speaks to the person with her.
A girl is opening a Diet Coke while talking to her boyfriend.
The drink does not have to be a Diet Coke and this person could be anyone, not just a boyfriend.
All drinks are not Diet Coke, and all people who speak to a girl are not her boyfriend.
Just because the blond girl is opening her drink as she speaks to the person with her, doesn't mean she is opening a Diet Coke while talking to her boyfriend.