I have 3B curls so maybe I can help. I have never heard of a Denman brush, but I would advise never brushing curly hair. When my hair is wet I don't do anything except blot it dry and put product in it. No comb, no pik, nothing except my hands to scrunch. I get frizz if I mess with it too much before it's dry. Maybe you can try a spray gel to put in your daughter's hair when it's wet, then let it air dry. If it's thin, it won't take long to dry and it may get rid of the frizz.
3b ringlets, very fine texture, chin length