Windows 8 Store info on puchases please

So I wanted to buy an app but I dunno how they work like if I purchase it on my account will I be able to log into my girlfriends account and have the app on there without having to buy it again? the app im on about is "Youtube RT" as its perfect for me but my trial has ran out.
if not could I not purchase it on my account copy the app folder to my girlfriends account?

Hello Cave, and welcome to Eight Forums.

Store apps are purchased and installed on a per specific Microsoft account thorugh the Store, and cannot just be copied over to another computer or account.

If you purchase a "Metro" app on your computer while signed into the Store with your Microsoft account, then if you were signed into her account on her Windows 8 computer, you would have to first sign in to the Store with your Microsoft account. Afterwards, you would be able to install "Your apps" to her user account on her Windows 8 computer.

The tutorial below can help give you more details on how to. Please let us know if you have any questions.

http://www.eightforums.com/tutorials/5270-apps-install-metro-apps-windows-8-store.html

Hope this helps,
Shawn