I don't think marie will have that much problems. Joachim is in a different position than he was when he first married or that his brother was in when Fred got married. Joachim runs an estate and that's where he will bring his new wife to live. Marie will be the queen of Schakenborg and Joachim will see to it, I'm convinced, that she can change there all things she wants changed. There is no mother-in-law living in the same house, no need at first to jump right into Royal life - I bet we won't see that much different pictures of Marie when she is married as we do now: attending private parties, a fashion show, a charity event. Different from Alexandra and Mary Marie will be able IMHO to grow slowly into Royal life, from the comfortable position of the wife of a husband who has formed his own life away from court and who will surely be willing to adapt his schedule and the way his home is run according to his wife's wishes and needs.
Plus I mbelieve that the way Marie lived and worked in Geneva might have prepared her for her new social position - she worked for the real estate/consulting/private equity-investment firm of her step father, right? If you make big money in Geneva, then you have to cope with the same kind of international clientele a princess of Denmark meets - only that the princess is higher up on the social ladder than the real estate broker or the investment consultant, so I guess it will even be easier for her than it has been so far.