Bulimia and anorexia are particularly difficult to treat even if you have the right specialists involved. Families of the sufferers need a lot of support too because dealing with it that close to you is very emotionally draining.
I think both the Spencers and the Royal Family pushed this marriage and that was a mistake. The Spencers had had their share of public and nasty family spats, particularly the divorce between Diana's parents. In addition to Diana's young age, I always wondered why her family situation wasn't a warning sign to the Royals. When Diana conducted a public battle with the Royal Family she was just doing what her parents had done before.
At any rate, I think the Royal Family has some problems with the way they are choosing their spouses. There seems to be prejudice in Britain against a member of the Royal Family marrying a non-Brit. When Charles and Diana married, the British press was fawning over the fact that she was an English princess. I personally found that offensive.
Its also problematic. In Britain, the Royals mainly socialize with the aristocracy and the British aristocracy has enough history of scandals, affairs, ruined marriages, and multiple marriages, and emotional neglect of children to make the emotional health of any girl coming out of this gene pool questionable at best. The Spencers are relatively more healthy than their close relatives, the Dukes of Marlborough so you can imagine how many problems the Marlboroughs have.
One thing has definitely come out of the Royal Marriages of the 90s. Any woman that marries into this family has got to have the thick skin of an elephant and be successful in internal politics. Marrying into the Royal Family is more a job than a marriage. Its similar to taking a job in a company in a highly charged political atmosphere where your job security depends on knowing how make your way among the key players.
Camilla seems to know how to play the internal politics within the Royal Family. I don't know about Sophie. But it will be interesting to see who the younger royals, ie., William and Harry end up marrying.