A study conducted by Playspan showed that when it comes to  mulitiplayer games, women spent $111 vs. $74 (when purchasing directly from the game maker) and $86 vs. $77 (when purchasing from a third party source).

With casual games that are usually free), women 40 percent more than men from 1st party publishers and more than three times as much from third-party publishers.

Playspan's CEO says, “It was also quite interesting to learn that women (37 percent) are nearly twice as likely as men (19 percent) to buy virtual item to decorate a page, persona or avatar."

source;  Playspan study