It's actually okay for a 15 year-old to date a 27 year-old in Hawaii. If anything MORE happens, however, there's a serious problem. The age of consent in Hawaii is 16. A 14 or 15year-old can legally consent to have sex with someone no more than five years older, but your 27 year-old friend is going to be out of luck in a major way.
You're both just a few years too late here. The age of consent in Hawaii used to be 14, but they changed it in 2001. Of course, in 2001, you would have been SEVEN, so there would have been an even bigger problem then!