[hocus pocus]

A lot of abusers will use threats to scare their victims into staying silent. Of course, all threats should be taken seriously but the intent behind them definitely does vary. Maybe you can talk to your friend and see what she thinks of the threats and of whether or not she feels like she's in danger because of them. Maybe you can encourage her to seek help and give her some time to do that, and then if she doesn't get help on her own you can tell someone about it. If you want to tell your mom but are afraid of her judgement maybe you can tell her but stay vague. For instance, you might tell her that your friend went through a traumatic experience or was harmed by someone instead of coming out and saying she was raped.