Ages of sex in New Jersey?

I am 18 and my girlfriend is 15, and will be 16 in about a month, but we were thinking of having sex. What are the legal stipulations of this? Is this legal? Can she charge me for statuary rape/sexual assault - Even if both her and I wanted to have sex? I know she is below the legal age of consent in NJ (which is 16) but I wanted to know if I can go to jail or pay a huge fine for something like this if she charges. Thanks!!