I recognise that you have a certain fondness for Diana, and want to blame the Royal family for her sadness, but I think it’s also worth considering Diana’s family and upbringing. She had a quite dysfunctional upbringing and difficult childhood and of her three living siblings, only one seems to be enjoying a stable life. One sister suffers from anorexia, alcoholism and previously claimed to have slept with 1000s of men, Diana was said to be estranged from another sister and her brother has been married three times and is said to be estranged from his older children. I think that Diana would have struggled in any relationship; she had at least half a dozen relationships that we know of and none of them sustained. If that behaviour had continued, it would not have been healthy for her or her sons.
Also, in the U.K. we consider 18 year olds to be adults, and although Diana may have been immature and vulnerable because of her upbringing and mental health, there is no reason to suggest that she was groomed.
It is a tragedy that she died so young. It is a tragedy that her family didn’t provide her with a supportive upbringing. It is a tragedy that she so wanted to be loved that she leapt into a relationship apparently without thought of the consequences and then desperately sought love with whomever was around her.
I am not absolving King Charles, Queen Camilla or the Royal family of all blame, but I do think it’s reasonable to argue, that because of the ‘baggage’ Diana carried, a marriage to anyone had only a slim chance of longevity.