My thoughts are lets the cops deal with it before you even touch the computer. If you do not know just what you are looking for or what logs may be about your own attemots to help could erase or alter inportant records that can be used as means to build a case against this person. Best bet while I hear about the Aunt and you a cousin, time to get Mom & Dad into the picture.

I'm still haing a bit challange here some parts of what you ask are not adding up at least for me. In general to many 3rd persons in the question. Just me and again if you don't know what your doing leave it alone for the people that do know.