Why don't you just cut it short? She can grow it longer when she is old enough to take care of it.

DD has a lovely pageboy (growing out now though) and it saves all the tears - looks much better than ratty knots!
lol your gonna laugh but... im growing her hair, as i am mine..for our wedding (when DF and i finally get to go through with wedding date - lol been put off twice - but she calls it "our wedding"... !

I did cut it about a year ago... myself and i was so upset. She has beautiful, curly blonde hair, i think that's why it is tricky to brush!!!