It turns out, tween girls are spending more and more time playing online games and become very engaged with the associated brands and communities as they do. For those looking to reach this demographic and reach into the pockets of their parents, there’s few better opportunities to capture their undivided attention.

Spil Games knows gaming. Particularly, the Dutch company is a leader in online and mobile gaming with more than 190 million monthly unique users. That’s comparable to how many people play games on Facebook, and it pretty much makes Spil’s first “State of Online Gaming Among Tween Girls” report released today required gaming reading.

While the stats and figures can be dizzying, this is never before quantified information that opens the possibility to draw significant conclusions. The findings were particularly revealing considering this has traditionally been considered a male driven hobby. Throw that assumption out the window.

The report is based on data collected from the company’s tween girls platform, GirlsGoGames. There, Spil has an audience of more than 7.6 million monthly unique users among girls eight- to 12-years-old and is the number one online destination in this category, 32 percent larger than its nearest competitor, Club Penguin.

Spil determined that more than 50 percent of all tween girls in the US now play online games, and that the amount of time they spend playing has doubled in the early part of 2012 to 78 minutes per month. Not surprisingly, the majority of this giggle, shop, giggle, share, OMG takes place on Saturday afternoons, with usage peaking at 5pm, before dinner time.

In 2011, GirlsGoGames hosted a total of nearly 1.1 billion games. Roughly one-quarter of these were “social” while the remaining 75 percent fall into the casual gaming category. The three most popular gaming categories for this demographic were, somewhat unsurprisingly, cooking, dress up, and test and quiz games.

More nuanced, the company shows that for girls in this age group, gaming is inherently social and interactive, like that of much of the rest of their world. Their gameplay regularly includes building friend lists, communicating with other users online, and sharing and creating content, like avatars and dress-up outfits. In fact, more than 88,000 such pieces of content are created each day; a higher per capita rate than similarly aged boys.

“It’s clear that for tween girls, online gaming is about more than just the game: It’s about being creative, cultivating friendships, and engaging with a fun community,” says Oscar Diele, Spil Games Chief Marketing Officer.

Spil reports that spending power among Tween girls in the US alone is at an all-time high of $260 billion. Holy Mary Kate and Ashley!

The company’s users spend significant volumes of real money on virtual goods within free-to-play games. Spil did not release specific spending figures for tween girls in this report, although it previously reported that teen boys 10 to 16 years old are its leading spenders at $60 per month.

“In the tween girl category in particular, it’s critical to develop a relationship directly with the parents,” says Spil VP of Corporate Development & External Communications Floris Jan Cuypers. Incidentally, these parents control the credit cards. He went on to say, “We strive to create memorable and enjoyable experiences, such as mothers and daughters playing together and even taking online gameplay experiences offline to the real world.”

Cuypers gave examples of baking recipes originally found in its “Sara’s Cooking Class” game or recreating outfits from “Shopahaulic.” Spil has succeeded in building trust with parents that its titles are age appropriate, educational so far as can be expected, and that it respects the boundaries of offering in-app purchase opportunities to minors.

Spil is not limited to tween girl gameplay. It is also heavily represented in the teen boys and family women categories, with its games played in 60 countries in 15 languages.

For advertisers and fellow game publishers, Spil is a welcome alternative to Facebook. The company has sourced more than 80 percent of its content from third parties. Unlike Facebook, which takes 30 percent of revenue and requires publishers to purchase advertising, Spil assumes all distribution risk. It has partnerships with companies such as Digital Chocolate, Bigpoint, and others to distribute third-party titles, and predicts that successful games could make $5 million in 2012 within the Spil platform alone.

The Dutch gaming giant has some big opportunities and challenges ahead, as it seeks to sustain its massive growth. It hopes to position itself more as an entertainment company, including merchandise and animation potential within its brands. Additionally, it is investing heavily in its mobile division, wanting to make mobile gaming as rich as its current Web platform.