Using iTunes match on a computer that has two libraries I was thinking of subscribing to iTunes Match. I share my computer with my sister who also has a iTunes library. She has no interest in iTunes match what so ever but I don't want her songs in my cloud. Can I:


Make a separate library under the same user account (on the actual computer) and only match one library leaving the other one unaffected?
Make another account on the computer, having the two libraries under different accounts, and only matching one library leaving the other one unaffected?


See what I want to do? I don't want my sister's library to be affected by the fact that mine is being matched. Anybody have any experience in this or have any thoughts?
In general it's recommended to have one computer account per user (in your case one for your sister and one for yourself), each with its own settings, home folder, iTunes library etc. This also takes care of separating mail, calendars, iTunes Match settings etc. without having to go through a lot of loops. 

In addition you need a separate AppleID for each user (especially if both want to use iTunes Match independently).