I live in a compound provided by my company and my colleague left the job. She also left some computer hardware item. She is a non muslim. I have her email address but she was never nice to me. She has also stolen some money from the company. Somebody just gave me one of the hardware Item to use. is it permissible to use this item myself? or shall I inform her and then use it?
It is simply ethical issue, you should do what seems the moral thing to do. Because, Islam teaches us to be ethical.
Seems like she left these things intentionally because she probably did not want them. But you should drop her an email to ask if she wants her stuff or you guys can use it.