Satin pillow cases and spray-on detangler or mousse or gel or water in the morning before combing, something that won't weigh it down, read labels. Fine, wavy hair needs a lot of tricks. My guy is almost 4 and has the most beautiful hair, but there's no way I can comb it dry in the morning. Spray or apply whatever you're using, (mousse or gel in your hands to rub it around and warm it first) comb through, then scrunch her hair to bring out the ringlets, I did this for years with one of my granddaughters. As she gets older you'll want to use shampoos, conditioners and treatments that specifically add volume and try braiding her hair at night before bed.
When she fusses tell her she's a princess (the satin cases) and that you're doing her "princess" hairdo. Or whatever she relates to. My guy has been into Jake and the Never Land Pirates about a year now, if he wants to bolt before his hair is done I tell him his "pirate" hair isn't done and he settles right down ;)