At DD's dance school they dont take them untill 3.5 as they don't think they are ready. DD goes to a really laid back dance school where there is not a big focus on costuming and concerts etc, which I really like as I am not personally into the whole makeup, expensive dance outfits etc for little girls.
Maybe if you want to trial her in some kind of dance you could look for a kindy dance program- where they get to do the dancing and music etc, without the pressure of the concerts.