That's nice, however a jury said said otherwise. The 17 year old is therefore irrelevant.
A 15 yr old cannot consent to anything.
So if a group of a dozen fifteen year old boys had sex with a single 17 year old girl, you'd propose locking her up on 12 counts of rape and letting them go?
Your "situational ethics" don't work.
This is probably the reason more rape victims don't come forward.