Why do you guys think that is? I haven't examined the list, but is it because she's losing her power, or is it because there are more and more women entering the list, thus pushing her down? I hope the latter is the case.
I suspect it has a lot do with Forbes being a business magazine. Most of the women on the list tend to be businesswomen or elected officials, both of whom control a lot of money and tend to get a lot of press mentions. These are Forbes's two top criteria for inclusion on the list (added to the bottom of this post).
As for press mentions, the magazine doesn't say which media it looked at. Did it only look at English-language media, for example? If so, that might have a lot to do with it as Rania appears to be getting less attention from the English-language media – especially the print media – as the years go by (if memory serves, she got the most press attention in the first few years of her husband's reign, when she had the novelty factor). Also worth considering is the possibility that the other women on the list might now be getting significantly more press coverage than Rania. A focus on the English-language media could also explain the large number of women from English-speaking countries in the top 100. Not a very inclusive list in my opinion, and one reason to take it with a grain of salt.
As for money, Rania probably doesn't control a lot of it via the Jordan River Foundation and can't be credited with Jordan's national budget since she likely has no say in how the country's finances are allocated. She does wield influence in Jordan and – to a lesser extent – internationally, but she doesn't match the sheer power that many of the high-level entrepreneurs and national leaders on the list exert in the course of their duties.
I also wonder how much Forbes has refined its methodology in the five years it has been doing this list. Even if money and press mentions remain the main criteria, how Forbes gathers and analyzes this information could have changed enough (or become more sophisticated) to affect which women are included and how they are ranked. Your suggestion that Forbes might be considering more women for its list is also something that is probably coming into play.
The World's Most Powerful Women - Forbes.com
We measure power as a composite of public profile--calculated using press mentions--and financial heft.
The economic component of the ranking considers job title and past career accomplishments, as well as the amount of money a woman controls. A chief executive gets the revenue of her business, for example, while a Nobel winner receives her prize money and a U.N. agency head receives her organization's budget. We modify the raw dollar figures to allow comparisons among the different financial realms so that the corporate revenue that an executive controls, for instance, is on the same footing as a country's gross domestic product, ascribed to prime ministers.