I think the problem is that you originally claimed that all you have to do is accept a Line contact and then they start taking money from your bank.
You then say that the victim clicked a link, downloaded an APK, ignored a warning, installed and launched an app.
That it a completely different claim than your original one. And while I am more sympathetic to your friend's plight than others on the forum (it's easier than some people think to get duped into doing something like that) it does make your original claim, and presumably the whole reason for starting this thread, invalid: Leaving your phone number lying aroud and subsequently accepting a Line contact alone is not enough to get scammed.
For anybody who is worried about the possibility of one of their loved ones being taken in by one of these scammers, there is an option in Line which says something like "allow people to find me by my phone number". Disable it. Now nobody can find you unless they know your LineID. This unfortunately isn't helpful, of course, for people who use their phone number as their LineID.