She is 17 and so she has not reached the legal age to make her own decision yet..
She definitely needs to tell her parent about it.. Yes the mistake has been done so there is no way to undo it... So to tell the parent is must... If they get violent or physical than you have option to save her by telling your parent or some one who can interfere and stop all that..
But the first thing is you need to counsel your friend and help her to get calm down so any suicidal thought or action can be avoided and talk with her about couple of options and help her to be strong and take decision. If you cannot handle this than you must take help of someone else who can be mediator between the girl and parents. Hope all things work out well
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