If you talk with the parents of other fifth-grade girls in your daughter's class, you will probably find that the friendships of all have changed this year. Fifth grade is a tough year, with many girls approaching puberty and feeling the first yearnings for independence. Often girls who have been close friends since kindergarten suddenly don't want to be friends with one another in fifth grade.
You can always talk with the school counselor if you continue to be concerned about your daughter's lack of friendships. He or she may be able to give your daughter some individual time or include her in a small group on making and keeping friends.