I know someone that is 17 and she is dating a 20 yr old boy. If she is still underage can he get in trouble for statutory rape? And does she have a say in matter?

Depends on where she is. However 16 is the age of consent in most places. So she is probably over the age of consent. Whether she has a say depends on local laws. In some places if the prosecutor is presented with proof of statutory rape, they must prosecute.

If she is underage for that area ( you did not say where they are at?) then yes, if she is underage to give consent then he can be changed with rape and be classed as a sex offender for the rest of his life)

It all depends on the area I live in Missouri and at 17 its her choice. Also I don't really see a problem. 17 and 20 is not a big difference... would you be worried in a year at 18 and 21? At 17 I think someone is perfectly capable of making there own decision in the dating department.