Help, iTunes removed content purchased by someone else.

My daughter received an ipad from my sister for Christmas preloaded with a movie, some games etc. I was trying to download the vlc app so I can put some videos on for her but every time I tried, I was told to either erase or transfer the content. I cannot transfer the content as I was prompted for my sister's itunes account which I don't have, and I didn't want to erase anything.

As I was experimenting I managed to sync the downloaded vlc app without being prompted to erase or transfer so I clicked ok. However, when it sycned, I saw content name listed that was being removed! To my surprise games and apps were removed but the one movie was not. I noticed that during the sync the ipad was backed up. I restored from the backup but the purchased content was not restored!

Is there a way to get the content back? I assume If I connect the ipad to my sister's computer she can restore it from her itunes but is there a way I can get it back now? Also, if she types in her password on my computer to authorize her account to allow me to transfer her content to my pc, will that allow me to make a purchase with her credit card on file with itunes or it just gives the right to download her content to my pc? I don't want to have the responsibility of having access to her itunes account.

It would be great if I could restore things without my sister, now.

I read the FAQ and the beginner thread but did not see anything on DRM mentioned.

TIA

If someone registers their iTunes on your computer, it does not give access to their credit card, nor can you purchase from their account. It only allows you to watch/listen to items purchased from their iTunes account.
As to the files you lost, if you allowed a backup before you synced the iPad on your computer, you could restore the iPad. Another way is to have your sister put it back on via her computer OR load the films on your computer and authorize your computer, which in my opinion is the best.
n.b. Your sister can authorize your computer, copy film/shows to your computer, sync iPad, and de-authorize computer. As long as you do not sync iPad again before the film/shows are watched, you will have no problem. You can only authorize 5 computers to 1 iTunes account.

I will have to try and transfer them from her pc to mine and hope that works. If the drm is not embeded in the actual file that should work.