In a film, certain conventions are used to build interest, to develop character, and to move the story forward. They usually have nothing to do with reality at all.

Just because I am sort of that way, I like to know about the reality, so I google something like, "The Iron Lady-what really happened" or some such. Generally, someone has gone through the movie, either with broad strokes or point by point, comparing what really happened with the film. It can be very entertaining.