We don't know anything. She was married to the most "Me First" person in the world. And she did have poor judgment, otherwise she would have fled from her marriage to a man who had a mistress, he, actually, loved and still does. It is not his fault, he was raised to think who could have both.
I agree we don't
don't know what happened. I don't believe Charles had a mistress from the start of the marriage and, since Diana never claimed to walk in on them, she really didn't know either. They both seemed "me first,' but Charles a little less than she was. Charles was able to refrain from attacking her publicly because he, unlike Diana, put William and Harry first.
Regarding Hasnat Khan, I agree with Warren that a lot of the attraction was that he was a doctor. Diana really wanted him to establish a clinic in Africa or Pakistan, which she would try and use in order to her maintain her image as a humanitarian.
I don't think it would have worked for Diana to go with him to a third world country, even after Harry turned 18. Very few people can maintain that level of commitment, even if they don't have a mental illness. I think she did better fundraising and drop by visits. She raised a lot of money and made a few people feel very special.
If she had lived but hadn't married Khan, I still think that there would have been a lot of suitable men for Diana. A lot of wealthy people, athletes, actors, businessmen, aristocrats, etc..., would have enjoyed the attention she attracted. Look at the Fayeds.
I like to think that she would have sought help for her illness and then settled down with a great man and found some measure of happiness. Her life wouldn't have been perfect, but I think she could have found a niche in the world when she realized that she really needed self-confidence, not adoration from people she didn't know.