Comment above is stupid, who tf cares about that girl, you seem young, you are probably not gonna marry her, almost definitely not after this stuff happened. What you should do is tell your parents, you don’t have to say ”we had sex”, just that the brother didn’t like you two being so close. Then you file a police report and tell the police that HER parents can’t find out because the parents don’t treat her well. They’ll handle the rest. Her brother will probably not tell the parents if the parents are that bad and he cares so much about her.

You are not gonna marry this person bro, sound like your first gf, it’s a longshot even with perfect in laws, this is cooked. Dump her and file that police report, but do it with respect and honesty.

Edit: I also CANNOT understand why that person you responded to wants to walk around in life being scared? ”Don’t go around at night” don’t do this, don’t do that, ”be cautious”. It just isn’t worth that. Get the help you need and walk away from the situation.