Looking to help a very good friend of mine put away their attacker

Location: Minnesota

TW: Rape, kidnapping, verbal and physical abuse, stalking

Also, forgive me if I am unclear and ask any clarifying questions necessary.

Myself, the victim, and the attacker all have resided within the state of Minnesota for the entirety of these events. The attacker is a friend of the victim's family, and have been in close contact pre-assault many times as young children. The assaults began while both were still minors, but both sets of parents have looked the other way. The attacker's parents have a LOT of money and will likely quite far to make sure their child doesn't see prison time. The assaults have continued periodically to this day, and as far as I know each instance has remained in-state. On several occasions the victim has found Air Tags in their car, and the attacker sends messages from burner phones and accounts semi-frequently. I will not go into the heavy details here but please understand that the victim has been kidnapped, forced into unwanted sexual acts, tied and starved, wounded in horrible and permanent ways among other things. The victim has informed me that she has been gathering evidence but she believes the courts will give her a very hard time with this. She has taken him to court alone as a minor, and landed a restraining order. However, the attacker is unfortunately not stupid and kept a perfectly clean slate during that period, but that was years ago and more evidence and abuse has accrued since that period ended. Again, this is a continuous and recurring series of events, so any and all recommendations will be heard. I plan to personally talk to the victims parents to attempt to bring them on board, but that's about as far as I've gotten. I have no legal experience but something must be done. How and where should I start?