I highly recommend that you read Antonia Fraser's biography of Marie Antoinette. Although Fraser is a biographer in the literary style, rather than in the formal academic style, her work is accessible and thoroughly researched, if occasionally making assumptions about the queen's emotional state and responses. (There is also a lengthy biography by Evelyne Lever, although as I haven't read this I can't vouch for it).

Fraser essentially concludes that the 'Madame Deficit' characterisation of the queen was partly justified, and partly exaggerated. Marie Antoinette was undoubtedly extravagant, especially in the matter of clothing, hairdressing, decoration and furniture. According to the courtier and diarist Madame Campan, an annual allowance of 100,000 livres was allocated to pay the queen's dressmaking and millinery bills, and this was frequently exceeded. This doesn't begin to take into account her gambling debts, or the cost of building projects such as the Petit Hameau (model village) at Versailles. A low-ranking government official might expect an annual salary of anything between 1500-2500 livres, for comparison.

However, Marie Antoinette's spending has to be seen in the context of the wider court, and indeed of France's wider financial problems. All senior members of the French royal family maintained their own, expensive, household establishments, with money lavished on clothes, art, horses, servants, gambling and the like - Marie Antoinette was not unique in this regard. Furthermore, although court debts were certainly unhelpful to France's national finances, they were not the root cause. By the mid-1780s, the French national debt was in the region of 12 billion livres - exacerbated greatly by the cost of French intervention in the American War of Independence. (For a detailed discussion of the financial context, see John Shovlin's The Political Economy of Virtue: Luxury, Patriotism and the Origins of the French Revolution, Cornell UP, 2006).

In that respect, Marie Antoinette's actual expenditures, although not helping the situation, were a drop in the ocean. It's worth pointing out that she made large philanthropic donations; also that the industries of fashion and luxury goods acted as an economic stimulant thanks in large part to her patronage. But by and large, her main problem was one of perception - regardless of whether or not her actual expenditure was the root cause of France's financial problems, her public-facing role, the attendant expectations of grandeur, and arguably a combination of mismanagement and bad luck, caused sections of the French public to cast her as a kind of cultural and financial scapegoat for a much, much bigger problem.