I second what Pholi has said - I always had issues with knots til I learnt how to deal with them. Just to add to what she said, definitely remove all knots before washing, but also comb the conditioner through when in the shower/bath before washing it out - makes it so much easier and more pleasant afterwards.

Another suggestion, I know your DD is young, but how is she at brushing her own hair? I've always found it hurts less to brush my own hair than when someone else does it. Even if she managed to get some of the initial knots out.....?????