You've taken a group of 4-year-olds to the park, and one of them starts crying because the others won't play with her. What do you do?
Stay out of it; let the kids deal with it on their own.
Talk to her and help her to figure out ways in which to get the other kids to play with her.
Tell her in a kind voice not to cry.
Try to distract the crying girl by showing her some other things she could play with.