The late Princess of Wales did a pretty good job as a senior member of the royal family and future Queen, IMO. She supported The Prince of Wales in his role as future King with the best of her ability. She was young but she got on with the job. Accompanied Charles on official engagements around the UK and Commonwealth and she took her royal role rather seriously.
Diana, did enjoy country life, she pretty much grew up in the country. She like Sandringham more because she was born on the estate at Park House. Diana didn't like the royal hunts, although she did kill a stag but cried afterwards. She enjoyed classical music and was taught to play classical pieces when she was a little girl in school. A talent that never left her. She also loved the Opera. If Diana & Charles was at Kensington Palace and famed tenor, Luciano Pavarotti was performing, they both would go over and watch him, even in the rain.
Diana didn't like horses much, mainly due to her falling off a horse as a child.
I agree that Diana did well in the public eye, but I disagree that she did well as a member of the royal family. My understanding is that supporting members of the royal family are not supposed to outshine the Queen or the Prince of Wales. Diana did-and she continued to purposely outshine the Queen and Charles even though she knew it was hurting their marriage.
I think Diana and Charles deceived themselves as much as they deceived each other. Charles deceived himself into thinking that he could make Diana happy even though he wasn't in love with her. He should have explicitly spelled it out and let Diana make the decision.
For Diana's part, I think she had a crush on the Prince of Wales, but wasn't really in love with Charles. She was young and had a romanticized view of him. Some people think he should have realized that but, although she was a bit giggly, she was also polished and refined. She had grown up around the royal family and surrounded by wealth.
I think he truly thought it could work, but the biggest problem is that they didn't have much in common because I strongly disagree that Diana enjoyed country life. I think it was fine as an occasional change of pace, but she really preferred being in the city and going out to nightclubs and shopping.
During the courtship, I think she convinced herself that she could be happy fishing, hunting, hiking, having quiet dinners with his friends, and watching him play polo. However, I have to acknowledge that she did not deceiver herself about enjoying polo, she hated it and knew it. Charles didn't know that. If he had, there probably wouldn't have been a first date much less a marriage.
Regardless, she was a very fascinating woman and she raised a lot of money for charity. But, as others note, every member of the royal family raises money for charities, and Diana had pretty much retired from charitable work soon after her separation.
She was an affectionate mother, but I don't think she was a good mother. It was inappropriate for her to use William and Harry to generate photo ops, and it was really inappropriate for her to use William as a confidant. She never considered the impact her public attacks on Charles had on her children. Some people tend to try and create a false equivalence, but Charles never publicly criticized Diana, and even told his friends to refrain from attacking her. I'm sure there were some exceptions, but most of the war was waged by Diana.
The real fascination was her beauty, clothes, and charisma. She truly drew people in, and people will probably continue to talk about her for at least another 10 years.