Did the producers forget that we have multiple pictures of the Queen from back then? It kinda breaks the realism. They should have cast an ugly woman or a good looking horse instead.
They knew very well that they were making a movie, not a history lesson, and nobody wants to see a movie about an ugly woman. In 1959 there was a movie named "Charlie's Aunt" based on a well known play about an ugly woman. You never saw it, did you?