Dear Embassy, how can I get visa to go to China if I am a girl of 19 years old?

I and my dad with my younger sister want to go to visit my relative in PRC for about 15 or 16 days. But when I went to buy flight ticket, the tour staff told me that I and my sister really difficult to get entry permit to go there because Chinese Embassy have a new law now. So Can you tell me, What should I do to get entry permit to go?
I hope you can give answer to me soon because I plan to go there for long.

Thank you for answer and help.