Even though Lizzie speaks English (and it's implied that Queen Victoria is absolutely fluent in English), Queen Victoria speaks to the nurse in a strange, made-up dialect. It's a very overt way for Victoria to show everyone, Lizzie included, that Queen Victoria thinks Lizzie is stupid and uneducated. Similarly, when Victoria won't let Lizzie outdo her, it shows that Ila's family is somewhat anxious about
looking wealthy and properly performing the image of wealth.