Describe the childhood incident when Anne got so furious with her mother and sister that she struck her tongue out at them .Why wasn't Anne able to get over this incident

Here is a quote from the text:

“It was on a day that I had to go to the dentist. Mummy and Margot were going to come with me and agreed that I should take my bicycle. When we had finished at the dentist and were outside again Margot and Mummy told me that they were going into the town to look at something or buy something-I don’t remember exactly what. I wanted to go to but was not allowed to as I had my bicycle with me. Tears of rage sprang into my eyes and Mummy and Margot began laughing at me. Then I became so furious that I stuck my tongue out at them in the street just as an old woman happened to pass by who looked very shocked! I rode home on my bicycle and I know I cried for a long time. It is queer that the wound that Mummy made then still burns when I think of how angry I was that afternoon.”