Toddler hair - help

My daughters hair will not grow. It's very thin and brittle. Ive tried different shampoos and conditioners, leave in conditioners, coconut oil, argan oil. Nothing seems to help. As a result she always looks like a mess. I can't really get it up since it's so short. It's to the point where people have asked why we cut it or why we don't brush it which is beyond annoying. I'm officially the mom with "that" crazy haired kid and I have no idea what to do. We bursh it with a comb gently and two minutes later it looks like we did nothing. Any tips out there on how to tame this mess?