You need to be sure about your girlfriend, if she is cheating or not. Find out what mysteries and why she is not ready to introduce you to her family. And if you are sure she is cheating on you then you should not continue your relationship, many people speak false, so that they get a potential partner, we cannot trust people only with their words, therefore my brother suggested me to take professional men dating services who keep complete information about their client's profession, relationships so that we can't be fooled and to better understand the person before making any decision.