Well, I see it as so;
Firstly, there's Maria's role as head of the family which she's invented for herself. Her predecessors never really got the chance to do so because they were barred from visiting Russia let alone meeting with Russian officials. To me it seems that she's modeled herself on other exiled monarchs who continue to do the more social role of the job without the paperwork and the political duties. Let's look at part of the role Queen Elizabeth II plays. She travels around the world opening exhibitions, meeting people, representing her country etc. Well, Maria does the same. Whether she does this to represent Russia or the Romanov family is debatable but I'd say Maria's view is that it's done to represent Russia more than the Imperial Family. The Russian authorities obviously have no problem with her doing what she's doing. However, how many of these duties does George take on? I find it strange when people accuse Maria of holding her son as some kind of prisoner. He's hardly ever with her, they don't live in the same country (she's in Spain, his work with MMC Norilsk Nickel isn't located there AFAIK) and he doesn't accompany her when she makes her various trips. A quick look through the photo albums on Maria's website show how much she does by herself.
Now this negates the point that she won't let Georgi live his own life. Indeed, I think Maria hopes that he can enjoy independence and freedom from what she considers to be the role of the Imperial Family until he inherits. People will say, "inherit what?" but that's a whole seperate debate about the worth of the role the Imperial Family now plays. It may change when he gets married of course but for now, I think she takes the view that he should gain experience doing things he enjoys doing. And if we were talking about any other heir from a reigning family, the jobs he's had wouldn't be considered unsuitable training. So I disagree that her whole existence is tied to him. I would however agree that she has spent her life building a dynasty.
And I actually believe that to be a good thing. Most countries that had monarchies now utilise their royal families in some way (even though they remain republics) and I think there'll always be affection for them. It'd be easy for the Romanovs just to disappear and to pretend they aren't who they are but surely it's of more benefit to help in any way they can? And Maria's been careful to show her dedication isn't financial. In fact, all she's done, she's done without financial reparation. There's been no salary granted to her and though there are lots of Russian associations/organisations/leagues that happily fund her visits to them in Australia, Ukraine and the like, she must be very dedicated to want to keep doing what she's doing.