This is a very important information which must be addressed more widely for proper understanding and misconceptions of underage young women. There is surely huge amount of dispute about the sexualization and abuse of underage young women in these difficulties just as you've stated but we also need to realize the fact that some young lady aren't really too young to get married.
There shouldn't be any form of molestation or sexual abuse to be experienced by any young women and any man involved in such act should be severely punished. We need to realize that some ladies are already mature in terms of their body size and character. The sad part about this is that these set of ladies maybe in dire need of a husband to start making their own family but environmental, family and peer pressure tends to obstruct then from achieving their goal which makes them want to engage in secret activities like masturbation or fornication just to satisfy their sexual desire.
We tend to see these set of matured ladies as underage while they themselves don't believe they are underage. They actually need to learn more about sex education which is actually the duty of the parent to educate their daughters regarding this aspect. There should also be free interaction between parents and daughters such that they allow their daughter to pour out anything going on in her mind without any fear or punishment from parent.
In conclusion, I believe we can reduce the act of immoralities that may be going on in the life of every young ladies by increasing their level of Spirituality in the Deen and giving them proper education and advices that will shapen their lives.
Thanks for reading and I hope this helps.