When my son was 4, he had anxiety due to existential concerns and his realization that death is a part of everyone's lives, including someday, his parents. What we did, due to a good pediatrician we had was to step up the rigor of his structured physical activities so that he had enough exercise to tire him out, give him endorphins and give him goals to focus on. This was in the form of Junior Swim Team, Martial Arts and basketball with a coach. I suggest that in addition to all the play that your daughter is getting, to add in a structured and routine physical activity that will make her tire out physically. That helps a lot with anxiety management.
