M (plus her baggage) chose to marry H (with all his well publicized baggage) because there was rather a lot in it for her. It was obvious that H could have easily found somebody more compatible but as a waning star which had never risen very high in the celebrity world, would she get another chance to marry somebody from such a wealthy and influential background? She knew that it was a one-off chance regardless of the obvious difficulties it would create for everybody else.
I never realised until recently that it was not such a whirlwind romance but an engagement following two years of courtship during which time they had experienced a battle with the press and with royal security. She had stayed on the royal estate, met his family many times. Her friendship with Eugenie predated this relationship.
If she was already bullying staff six months before they were even engaged then it is obvious that she had fully sized up the role which came in exchange for all the title, designer goodies, palatial homes and publicity.
It is dishonest to state that she never knew what she was getting herself into. It was a calculated decision she took because the benefits were attractive. Her way of suppressing the critics and doubters was to grab the power and put them in their place.
I wish that the RF had not made any major concessions for her in the beginning. They should have honestly told her that 'This is the security available, this is the likely level of press scrutiny. There is a dull job attached to the privileges and the title. These are the rules. You cannot change them, we don't want to know. You cannot merch. You can't have a £30m white wedding. You need to be polite towards staff. Take all of it graciously or let it go'. Not many of the difficulties emerged later on.
There was definitely an expectations mismanagement on both sides which left her expecting special treatment and special concessions. When this never materialised to her satisfaction, it was replaced by a resentment which almost too deep seated to resolve.