She may have been only 19 when she married but her family must have advised her very clearly what she was getting into; she did not marry for true love, she married Charles for a clear purpose. Diana was pretty (which seems to be more important than anything else in modern society) so the public took her into their hearts, but she was a vacuous air-head with eating disorders, not something we should aspire to.
The Royal Family should be strong enough to make unpopular decisions. If William and Harry can accept Camilla then so will the rest of us. Who wants a Royal Family commanded by the tabloid press?