Since there are no children in your neighborhood, you'll have to work a little harder to provide those opportunities for her. Contact the parents of some of the children in your daughter's class and work out days and times for them to come over to play. You may be able to schedule some regular play dates, or perhaps you and another mom could take turns letting the children come home after school and play together.
You may also want to set up opportunities for group involvement for your daughter. Joining a Girl Scout troop or a soccer team would give her chances to meet other children with similar interests in an informal setting.
Talk also with the school counselor. He may be able to give your daughter some individual time or include her in a small group on making friends. The teacher can also help encourage friendships on the playground and in the classroom.