The Iron Lady Movie - perspectives?

So, my Mother passed away at 90 years old on 1/6/12, after having dementia type symptoms for a number of years (15+). 9 days later, my brother took our Father and I to see The Iron Lady movie, which is about Margaret Thatcher's life (former UK Prime Minister). I had no idea that this movie had been done from a completely different perspective from other biographical movies - rather than being a timeline (starts when she's young, goes through her family life, career, and retirement years), it was done from the perspective of dementia type flashbacks. Of course, if was a poor choice of movie for me to see, much less our Father (they'd been married for nearly 62 years, and it was a love affair through to the end). Was any research done on this movie that shows that the behavior that MT (Margaret) exhibits in her dementia is in fact her re-living some of her earlier life, or was this just writers' and directorial license. It is a very good movie from the perspective of showing what may be happening in a person with dementia, and certainly fit with some of the actions and words that my Mother displayed her her last 4-6 weeks of living - she died from a very large mesenteric tumor which cut off the blood supply to her intestines. It's likely that the dementia she had been displaying for years was due to a short circuit in her brain where pain was actually creating dementia like behavior. Thank you!