There are so many books, articles and videos to use as sources for this one but the book on Diana by Anne Edwards and the one by Sally Bedell Smith are good ones. The videos "Diana: In Search of Happiness" and her own Panorama interview provide the information cited below.
All explore Diana's illnesses and "mental instability." The Smith book goes so far to say Diana was a "borderline" personality or showed classic symptoms of it. She did not ever--by all accounts--"seriously" try to kill herself--the time she threw herself down the stairs while pregnant with William has been reported a few different ways with Diana changing her story from she meant to hurt herself to "I would never do anything to put my baby in jeopardy." She did injure herself using what is called "self-mutilation," where she used knives or razors to cause cuts and marks on her arms and legs. This went on during the early years of the marriage but decreased as time went on. This is not an attempt to kill oneself but rather a cry for attention. Her sister, in the Smith book, noticed. Charles knew about it, according to Diana--in the "Panorama" tape. A lot of Diana's problems--and I am not a psychiatrist nor are those who wrote the books about it--seem to stem from anxiety and depression (post partum and regular, if there is such a thing, depression). Depression is "anger turned inward" and certainly whatever was going on with Charles and Camilla or simply Charles being a bachelor for so long and used to doing what he wanted when he wanted, caused someone like Diana who craved love and attention a lot of irritation, which Charles did not want to hear and subsequently led to depression. She was very young, shy and not worldly when she married and suddenly having to speak in public was a big transition. That and simply trying to be accepted into the royal family led to a lot of anxiety. The bulimia has been attributed to everything from Charles squeezing her waist and saying "my, we're a bit chubby here" to her own fascination with her public image and fashion and wanting to be slim to look her best.
I was reading Paul Burrell's book last night. I think it boils down to this. Diana had a difficult childhood and wanted and needed a great deal of affection, approval and attention. The Royal Family takes its lead, in large part, from the Queen and Prince Phillip, who showed Diana a lot of kindness but tempered it by not wanting to be intrusive. Burrell describes a very good relationship between the Queen and Diana early on--whereby Diana might be alone at night and ask if the Queen was dining in. Whenever she was, the Queen would always ask Diana to join her. But the Queen does not hug and kiss and cuddle as effusively as Diana likely needed--so Diana would often interpret a pleasant dinner as another "cold" encounter. Its a matter of expectations and the difference in the way Charles, the Queen and others in the Royal Family simply could not live upto Diana's expectations. Quite frankly, I'm not sure--and I like Diana very much--anyone could. The attraction to Dodi was based in large part on the fact he had the time to devote to her and was, like Diana, an individual who craved expressions of love (his mother died when he was quite young and his father tended to give him money but not a whole lot of time). So, what you have is a cocktail for problems as Diana's neediness could only be sufficiently addressed when and if people would drop everything for her and give her unstinting attention--and, as one of her friend's pointed out in "Diana: In Search of Happiness," few are able to give that kind of love non-stop. A story in the Smith book regarding Oliver Hoare is telling. He was separated and gave Diana a great deal of attention. Then, one day, his young daughter was ill and he had to cancel a get-together with Diana. She flew off the deep-end and--to make a long story short--he became so worried, he was forced to ignore his daughter in order to search for Diana. He found her crying in Kensington Park on a bench--convinced his need to see his daughter meant she no longer mattered. So, she was a difficult person to befriend or be involved with. And that is a shame. Another close friend, Lord Peter Palumbo, said the simple fact she was "royal" meant you couldn't just drop in on her and led to an isolating existence--as she would be on public duties, surrounded by loving people who needed her then ended the day eating alone off a tray in her sitting room.
What ifs are easy....would her life have been more satisfying if she had not been a royal? Yes and no. She did love the attention and helping others and other "royal perks." But it also isolated her and led to complications within her marriage and personal life. One thing is for sure--there are no easy answers when it comes to Diana's life. And what may have happened to give her joy will never be known. I think that's what keeps her "alive" for so many of us as she is a puzzle and, in the end, we will never have the answers. In the end, even she didn't.....or so it seems.
Sorry for the long diatribe but it is a complicated issue. I do not believe she would ever have killed herself, however.