Follow your dreams.... tell your mom you don't have a wife and family to support lol... you'll never know until you try...

Maybe a better wording from your mom might be: To be successful as a professional actress or actor is a mathematical long shot. Also, the bulk of reasoning as to why success is achieved, or not, is determined largely on factors beyond the control of the individual chasing the profession. In other words no matter how pretty and talented you might be it's still a very very hard profession to become successful in. Now, having said that, I sincerely doubt your mother is telling you not to try. Absolutely try with all your might if that is your passion. But just in case, have a solid backup plan!! I think, that's all she's saying!! Good luck to you!!