"Wanna be Friends?" joke

A blonde was walking past a schoolyard during recess when she saw a young girl standing all alone on one end of the soccer field, while the other children all played a game of soccer. Feeling sorry for the poor child, she went up to the girl and made small talk.
She asked the little girl if she was OK.
The little girl replied she was fine.
The blonde then said, "Why don't you go play with the other children?"
The little girl replied, "I already am."
The blonde, a bit annoyed said, "What do you mean, you already am?"
The girl replied, "I am playing."
The blonde, thinking the girl was lying so she wouldnt be embarassed, said, "Wanna be friends?"
The girl hesitated, then reluctantly said Sure.
The blonde, feeling she made progress, says, "Would you like to go play in the sandbox?"
The girl replies, "Sure... after I'm done playing soccer. I'm the goalie."