It's the writing of a simple, good-hearted or good natured "humanitarian". Her writing is economical but with creative flourish. It shows her strong intelligence in the way she alters and shortens or changes her letters of the alphabet to fit the fast workings of her mind. Her writings also show stability and consistency. She was not as "changeable" as some have said, but if and when she was harassed or felt harassed, I am sure she did have a temper. Which would have been natural for her strong-willed and artistic personality. .
The inconsistencies of character were not so much within herself as they were viewed as inconsistencies with her role. The passive and humanitarian role of healer and nurse and servant influences public and common perspective of intelligence. It is thought someone may have a very good "heart" to do such work, but may not need to be particularly brilliant. And yet I think she was both, and when she was interested in a subject, she was able to prove this by immersing herself and learning a subject thoroughly. When she became interested in the field mines, she was able to blend both her activism and concern with her intellectual abilities. She became passionate enough about it to apply herself, and in doing preliminary research, came across information which both shocked and spurred her on, to know more. She was engaged, and some did not like the fact that she had become so engaged.
She was not only persuasive, and had a way with people; she was smart. She had the ears of the world, which has been said before, and is something everyone knows. She was a woman who had become a problem. Not because she had "mental problems" but because she was getting involved in things she should not know about. In addition to the complications with being both a princess and an artist, was Diana's marriage. She couldn't fulfill the desire she had to be an artist in the capacity she wanted for herself, but princess did have an appeal.