Based on the information given, the logical conclusion is that Rachel won the race.
The statement "Rachel ran faster than Helen" indicates that Rachel performed better than Helen. Additionally, the statement "Darla came in last" suggests that Darla performed the worst among the mentioned individuals. Lastly, the statement "Helen finished ahead of Charlene" implies that Helen performed better than Charlene.
Since Rachel ran faster than Helen, Helen finished ahead of Charlene, and Darla came in last, the logical conclusion is that Rachel won the race. Therefore, Rachel is the winner.