The Rite of Christian Initiation of Adults consistently calls for full initiation when the person being baptized is either an adult or a child of catechetical age. This is repeated in the National Statutes issued by the all of the Bishops in the United States, and by Archbishop Vigneron as a policy of the Archdiocese of Detroit. This is the only way for the 4th grader to be initiated. The important thing is not doing something with other peers but rather becoming fully initiated into God’s family according the Church’s ritual. The expectation with adults, as well as, with children is that their catechesis….learning about the faith…will continue and grow for the rest of their lives. The young girl would be expected to continue her formation. Formation is not just for reception of a sacrament.
When it comes time for the other children who are the young girl’s peers to be confirmed it is advised that she, as a fully initiated member of the Church, will be able to have a role as a liturgical minister at the celebration. For exapmle, server for the confirming bishop, etc.