Two iTunes libraries with one PC?

Hi, how can I use two iTunes libraries with one PC? Yes, I know how to 'create' a new iTunes library (by holding the shift key) so please don't send me the link to that Apple Support page.

Okay, so recently my sister's PC crashed and she lost all of her content including her iTunes. Of course she still has the music/videos still on her iPhone so I want to create a new library on my PC but put her old music/videos from her iPhone into it. By the way, I have my own iTunes library and ID. I just want to put her old music from her iPhone into her new library.

So that way, we'll both have two different iTunes libraries on my PC and my sister won't be losing any of her content. Any help will be appreciated.