I'm still not clear what you are getting at.
Unless your 25yo friend has learning difficulties, she was fully aware of her relationship with a 19yo. She is an adult. She may have suffered domestic abuse or coercive control, but she is, and will be treated as an adult by the police.
In the case of young people (13-18), the police and schools have to tread a fine line, since the age of criminal responsibility is legally 10yo. If a child punches another at school, should they be charged with assault, sent to young offenders, wrecking their education & the chance of a decent job etc? If reading them the riot act, being suspended from school and the wrath of their parents ensures they never do it again, then probably not.
The answer in teen relationships is for parents and schools to model good relationships, make it clear that there is help always available, that bullying & coercion must never be tolerated, and that the police are there if any offence is sufficiently serious. The Romeo & Juliet clause means a sexual relationship between a 15yo and a 16yo would not be seen as child abuse if consensual because the two people concerned are only a few months different in age.
Any non-consensual activity within that age group is still either sexual assault or rape.